Every guy should marry a 'Clean Freak'. When she asks: "Why don't you clean the toilet, or change the sheets, or vacuum?" You can easily reply, when it gets dirty to my standard or until you do them first. Actually you are not suppose to say (Or until you do them first). Just think it!
As for my sheets, it's about every week or 10 days. Heck if we changed them everytime we had sex, our washer could not keep up with the laundry.