It’s the first task every Saturday morning: strip bed; put on clean sheets and pillowcases; wash old ones.
Oh, you’re not the only one - back when I was on my own I would do that, but between how muddy I get at work these days and the way my Other Half sweats into the sheets it really does need to be at least once a week.
More often if the parrots get loose in the bed. No, no, it’s not just the mess they leave behind, they also like to hide stuff in the bed, like half chewed up food. I don’t know if they’re storing it or just messy, but they ARE messy.
We have housecleaners that come in every two weeks, and changing the sheets is one of their services.
The poll needs an option for every two weeks; “few” is totally different.
I can’t imagine having sheets on for months at a time, sorry guys. You might not have dirt and grime to grind into the sheets, but you definitely sweat and secrete skin oils.
On the other hand, twice a week is also nuts to me. Sorry, aruvqan! 
I guess I’m kinda grimy (but not as grimy relative to others as I feared, looking at the results), but I just don’t feel like they get that filthy that quickly So I only change them once a month or two (I actually chose once a month in the poll but I probably should have chosen every few months).
I know they’re surely coated in a ton of invisible dead skin and dried sweat and whatnot but as long as they don’t smell bad then I’m comfortable.
Of course, when I had a girlfriend who regularly stayed in the bed with me… we changed them more often. 
For me it’s not about going to bed dirty or the sheets smelling or anything like that. After about a week the sheets get kind of wrinkly and sort of loose, and washing them makes them all smooth and tight again. I like that.
(All of that sounds kinda dirty, doesn’t it?)
Once every few months, and then only because we’re usually having someone over and I have to give-up my room to them.
This always seemed normal to me, but by the looks of others’ responses this is probably a little gross. It’s never bothered me unless the sheets were obviously dirty.
Every couple weeks. I’d change 'em more if I had company more often.
I used to change them every Wednesday (even when I was single) and ideally I’ll still change them once a week, but right now we’re still adjusting to the new addition to our family and not everything is happening on the “ideal” schedule.
Clean sheets are one of the siple pleasures in life. I chose every week, but on occasion, if I get busy, it stretches out to 2 weeks. If I had the time I’d change 'em every couple days just because I love the smell/feel of fresh sheets.
This is it for me, too.
I used to treat sheets like litmus paper - when they change color, it’s time to do a wash. Then I got married.
Hot flashes, I sweat like a pig, and hubby has thyroid issues and gets night sweats as well.
Also there is nothing quite like freshly washed sheets, when you are broke you get to like simple pleasures =)
Every Saturday or Sunday before laundry, like clockwork.
If I forget (couple times a year) I still change the pillowcases.
I agree. I love bringing the sheets in from the clothes line, dry and beautifully fresh smelling.
Past few weeks has sucked to be you, then. You brought them in wet and frozen. 
(Last few days excepted.)
Once a week here in summer, or more often if it’s really hot cause humid night sweats make for gross sheets.
Once every couple of weeks in winter.
More often if we have a pet catastrophe.
Every Saturday without fail. If I had the resources and didn’t give a shit about the environment I’d have clean sheets every other day.
When I don’t have too much other laundry to do. And actually think about doing it. hard to set a time on that.
Every two or three weeks. I don’t really sweat much.
My dog and cat somtimes sleep on my bed, but on the cover over the duvet, which (cover) I keep there especially so that I can wash it more regularly, about once a week or so, depending on how often they’ve been in there.