This didn’t used to happen when we first built the house (about 10-15 years ago). But now it’s several times a week. My wife thinks the toilets are junk, but as above, it’s a more recent phenomenon.
So I’m wondering if there’s some amount of clog that never gets removed from plunging or snaking, possibly in the pipes, such that a smaller amount of waste clogs it up.
Does that make sense? And if so, what do you do about it?
Did you change brand or type of TP? Thicker strength TP tends to clog us up.
Public sewer system or septic system/tank?
What types of things do you flush or send down the drains in all parts of the house? Even tissues (for noses) can cause problems.
Do you know if your vents are clear? Blocked vents can really slow things down even if the sewer pipe in the house is good and clear.
If the plumbing is really clogged, a plumber might have to access your clean out points in the system, which basically involved unscrewing end caps and doing a real ‘roto’ type cleaning, direct into the sewage/waste pipe in your home or on your property. This is done in the basement, right into the waste pipe. No going 'round sinks/j pipes/toilets, etc.
The vents might require a similar/direct cleaning.
Any plumbing system has air vents. If these vents get clogged the water drains much more slowly and the pipes are more easily clogged. I don’t really know how you might check this (except maybe ask your plumber).
Oops. beaten to the punch.
I had a plumber out last month for a non-toilet issue. We were chatting and he said his next call was for a stopped up toilet. “They’re not going to like what I tell them,” he said “they need to get a new toilet.”
I asked him what he meant by that, and he said that if your toilet gets stopped up a lot or if it gets stopped up to the point where you need a plumber, then you need to replace the toilet.
I told him I thought that was weird…a toilet is just a vessel for water to go in and out. If it’s not cracked, why replace it? How does it stop stuff from going down? What’s the difference between a $50 and a $300 toilet anyway?
He said that the construction of the inside of the toilet is the difference in price, as well as the materials. If the toilet is collecting junk inside of it, it needs to be replaced. This will happen sooner/more often on a cheap toilet than an expensive toilet.
So, your wife might be right. It might be time for a new toilet, because yours is just plain gunked up inside.
Long ago, I moved into a rental where the toilet clogged several times a week. Turned the previous tenant had dropped a tootbrush down there, and it had wedged in the neck of the siphon. I got it out with a pipesnake. A plunger would not touch it.
It can’t be too far down the system because otherwise all the toilets would be clogged at the same time (as would the sinks, FTM). And I’ve snaked them many times, which always works to unclog them, but not to prevent a recurrance (which is another reason it can’t be too far down - unlike a plunger, a snake wouldn’t work on what it can’t reach). So I’m thinking maybe the snake is leaving stuff on the sides, but I doubt if it could be something like a toothbrush.
The only toilets that have this problem are the kids’ bathroom and the family one. The master bathroom does not. But I don’t know if this is due to different bathroom habits, or - more likely, IMHO - to the fact that it gets much less usage.
One thing I’m not too keen on is replacing a toilet. Yuck.
Supposedly tampons can also clog up the pipes along the way, and may take a while to build up to a “critical mass” of clogging. (Unbeknownst to most women, you probably shouldn’t flush used tampons.)
Not that bad. Helps if you have someone help you lift it. But it’s not like there’s a disgusting cesspool waiting below – all the waste gets washed away. You can stick a rag in the pipe while you’re working if you’re squeamish – just don’t forget to remove it when you’re done.
The time frame you have established also allow for tree roots coming into play with the pipes. Is this a possibility?
Are your toilet the newer/low flow units?
Is there a vent pipe for that area of the house? The vent pipe may have become plugged.
I second the idea of checking to make sure nothing “irregular” has been flushed. I have heard plenty of stories about rubber ducks, other kids toys, toothbrushes, pagers, etc getting flushed and later the realization that this is causing blockages.
You know that ad where they show people flushing down a bowlful of golf balls? Yeah, you shouldn’t really try that, either 
And the kids never use the master bath, right?
I’ve seen things get stuck inside toilets that successfully evade snaking - toothbrushes are in the Plumbers’ Hall of Fame for this. You can snake right past a toothbrush and not know it’s in there, but the next chunk of stuff will get stuck. Similarly, pencils, pens, popsicle sticks, mascara bottles, and similar long skinny things can do this.
Most often, the only cure is to take the toilet off and push the offending thing out from below. Yeah, I know. Ick.
Ten to fifteen year old low-flow toilets are junk, compared to what’s available now. If this was my house, I’d start by just replacing the toilet. I’ve had very good results with Toto. Eljer and American Standard also make “performance” toilets that are well-regarded, though I have no direct experience with them.
Another possibility is that the sewer vent is clogged, but that usually shows itself as slow flushing, rather than clogs, and sinks draining slowly and going glug-glug-glug. Usually, you have to attack this from on the roof.
We just put a Eijer in a totally new bathroom, and I’m having problems with clogs.
All the pipe runs were new, and the toilet usually flushes fine. But, I’ve had to stop flushing tampons, and my daughter often clogs the toilet with her poops.
There is no backup in any other sink or toilet in the house. I have no idea why this happens, but it drives me crazy, and makes me afraid we’re going to have to rip out all of the plumbing we installed to redo it 
A totally different possibility:
Back when my father was alive, I remember my mother mentioning that the toilet was getting clogged more than it had been . . . only when he had used it. The problem went away when he died. Apparently, as some people age, their crap can get thicker and/or more “solid.” sometimes causing blockage.
good flushing action depends on rapid water introduction and rapid air venting and rapid water discharge.
the toilet rim and siphon jet can narrow with mineralization and prevent good siphon starting. you can test this with a water flush, rapidly pour a bucket of water right above the siphon hole right after doing the handle. if this improves the flushing then it might be water introduction being the problem.
My toothbrush! I’ve been looking all over for it.
brushbrushbrushbrushbrush
Ah, nothing beats a clean mouth.
Hmmmm… maybe those two toilets are on the same vent? Are they above/beside each other? When the vent is clogged, you can get a gurgling as the flush surge sucks air down the drain from the nearby sinks and toilets. That’s a clue. If so, climb up on the roof and see if some stupid bird has built a nest which has fallen down and plugged tyour vent.
Roots are another problem; or if the sewer line is somehow damaged, and has been slowly collapsing in the yard; but normally that would be something that happens in the whole house.
It could be just poor flush volume as mentioned, especially if the other toilets are a cheaper brand/model than the master bathroom. I seriously doubt its “buildup” or you would notice it every time you snake.
Before you go and replace the toilet, try actually removing it (unbolting it and taking it off the waste pipe in the floor. Then look inside it – actually run your hand/arm* all the way up from the bottom and feel around to check for anything like a toothbrush, etc. caught in there. Also, if it feels rough inside the toilet, rather than smooth porcelain – that will be a constant problem: replace the toilet (with a better quality one). And look down the waste pipe (a flashlight may help) to see if anything is caught there.
Doing this, you are about halfway to replacing the toilet. So it’s best to do this on a day/time when the stores are open, so if you do have to replace the toilet, you can just run to the store and get a new one right then. And make sure you have enough time available to finish the project.
Also, even if you find something caught inside and remove it, you should consider replacing the wax ring that seals the toilet to the waste pipe. Anytime you unbolt & remove the toilet it’s possible that this won’t seal tightly again. And it only costs about $5, so go ahead and replace it before resetting the toilet.