I wash them and then put the same set on - that way I never have to fold sheets!
I can't get in bed at night unless the bed is made... so if for some reason it doesn't get made in the morning, I make it right before we get in (drives my husband nuts!)
In the winter I'll go up to 2 weeks but in the summer its once a week.
Unless of course some sort of accident occurs!!
The mattress pad is washed a couple times of year when I rotate the mattress and vaccuum at the cat hair off the edges of the box spring!!
I change mine every 2 weeks unless Brad decides to eat something like cookies in bed, then it's right after I find out because I can't stand crumbs in my bed!
I usually change mine whenever I notice they're starting to get dirty- it's probably every 2-3 weeks. I do the same thing as jeanor though- I have one set of sheets that I strip and wash every time. I usually wash my quilt at the same time too, I'm a thrasher in my sleep and i usually end with everything all twisted and the sheet on the top and the quilt on the bottom
Every 2 weeks or so here too! I have bad sinuses and allergies so I have to keep the cat hair to a minimum in the bed or I'll wake up all snotty and icky feeling!!