I’d guess I use a towel for about 2 weeks before washing. I’m really surprised that people use a different towel every day.
Humboldt, California. It’s humid and not all that sunny here most of the time. The towels hang on a hook in a room with windows, not under the direct sun.
ETA: Of course, it also depends on the type of towel. I have thin backpacking ones that dry in a few hours and also thick, huge, fluffy cotton ones that take days.
I use an REI Bath Towel. It’s amazing. It’s so thin and light and after I’m done using it, I’m so dry people don’t even know I’ve been in the shower.
I wash it once every two weeks or so. I’ve gone a week or two longer a few times but it starts to smell eventually. I’m not sure why. Maybe it’s from sweat after taking a hot shower.
Same here, which is usually about once a week. My towl rack is directly above the register for the heater, so my towel usually gets blow-dried each morning when the heat comes on.
I have a turbietowel for my hair, they came in a set of 3 - blue, pink and purple. Though I think they are cheap chinese knockoffs, I got them in the dollar store 
I wash my hair about every 4 days - I do not ‘process’ my hair with dyes, heat, crimpers or anything so it doesn’t get product glooped all over it so I don’t have to wash it more frequently. It is bra strap length and regular brushing distributes the oil properly over the length. I use them alternating, and hanging them to dry by the woodstove to dry them out. I wash them once a month, which works out to 4 or 5 uses per month with thorough drying between times. I also have 2 floor length tunics that I got probably 10 or so years ago from some fat broads catalog that is effectively 2 huge towels sewn together at the sides and shoulders leaving holes for neck and arm with a pocket set into each side seam. It sounds ugly but it is not. I slip into it and wander back to the bedroom. By the time I get there [all of 20 feet] I am pretty much dry and I can get dressed. I was told not to scrub my body or face dry, it can do microscratches and as a diabetic, I don’t need any more inward ways for microbes to try and infect me. I also hang these to dry between showers, they get washed about every 2 weeks - I do not shower every day, dry skin, unless I do something that gets me dirty or sweaty. I shower alternating days.
When I lived at the old house, I’d change bath towels every two days—occasionally three, but by the third day I could usually smell the difference. But that was when I had to take baths because the house didn’t have a working shower, so I probably didn’t get rinsed as clean (of dirt, soap, and dead skin cells) as in a shower. Plus, the bathroom wasn’t all that well ventilated.
In my current apartment, and at my fiancee’s house, I can get away with using the same towel for much longer—maybe about a week.
Assuming you have a decent sense of smell, I suggest the sniff test: if the towel smells clean, and feels okay, go ahead and use it another day.
Where do you live, the face of the sun? My towels take a lot longer than that to dry.
New York. Maybe it’s over an hour – I checked mine after having taken a shower about forty minutes ago and it’s still a bit damp but I’m guessing in twenty or thirty minutes it should be fine. I mean, they’re towels – getting dry is their job.
OMG! Thanks, guys! I feel I can finally use my good towels. I will check them for odor daily and hopefully I can get away with using one or two per week, which means I can toss them in with the sheets weekly and save that extra load! Woohoo!
I don’t have skin issues or anything. It’s just how I was brought up–a new towel at bath, change the hand towels and kitchen towels every two days. After I would try going for a couple days reusing the same bath towel I just would start to feel like it was unhygienic or something, or maybe going against what my mom taught me?
I was just wondering what the regulars I run into at the laundry room think when they see me putting all those towels in the wash–that there must be several people living in my one bedroom apartment?!!
Thanks so much–this has made me feel better. 
I make those myself, out of cheap cotton towels of just the right thickness for hair drying. I love them!
I wash our towels about once a week, too. Since there is just the two of us, they don’t really make a load, but you don’t have to wash something as soon as you change it - sometimes I chuck them into the laundry room until I can make a towel load.
I don’t recommend doing that. Even the nicest towels are made of much coarser fibers than your sheets. The towels will make little microscopic cuts on the sheets and cause them to wear out much faster. And sheets, they are expensive to replace.
I change towels on Mondays and Thursdays. I’d love to move up to 3x a week, but it would be too decadent. 
Our towels dry on the rack (heated towel rack, what is that??) but there’s not as much space as there should be and they’re pretty squished so it takes about 12 hours for them to dry, esp. in winter. I think if I left them for longer than 3-4 days they would start to smell funny.
Taking this to its logical conclusion: I wring out the washcloth and dry myself with that as best I can. This removes all the loose water, leaving me just a little damp. Then I simply air dry. (Myself, that is, not the washcloth. Well, then I hang the washcloth to air dry too, but it goes into the laundry after that.)
I never have to use any of my towels.
Izzat really true? I’ve never heard this. (The coarse fiber/micro cuts thing. Not the expensive thing - that I can easily find out for myself.)
I prefer to use a fresh towel each time I shower. This is because rarely do towels hung up in our bathroom get fully dry in between showers. The feel of a not-quite-dry towel gives me the creeps. It has nothing to do with whether the towel is dirty, but in how dry (or not) the towel is.
I don’t mind doing the laundry (in my own home) and we don’t pay per gallon or however water is charged, just a flat rate.
I use mine until it smells funny. Same with the washcloth I wipe my face with after shaving. There’s no set time limit for it. If it smells bad after I finish drying off I toss it in the laundry.
I get irritated (literally!) by the incredibly dry air here, but at least our towels dry fast.
New towel every time, previous towel gets reused on the floor as a makeshift bathmat.
I haven’t run empirical trials my ownself, but I’ve read this in several different housekeeping books. Sheets, all cotton ones anyway, are made of lovely silky fine fibers. Towels aren’t.
Another one for about a week. I also use a smaller, thinner towel to dry my hair when I wash it (a couple of times a week in winter and daily in summer). It gets thrown in the towel basket along with the bath towel and a hand towel. When the basket’s full, I do a load of towels and washcloths.
Washcloths, on the other hand are a one-use-before-washing item. I wring them out, hang them on the hook in teh shower and they’re dry when I replace it the next morning, to be thrown in the towel basket too.