Hello M.,
Tax/bank papers: 7 years
House repairs/maintenance/improvements: keep indefinitely or until the house is sold.
Utilities: I keep the one from January every year. The only reason I do that is because someone at work had to prove residency from several years back and that's what she needed. go figure!
The past couple of years I've started scanning my utility bills and also recording the info in a spreadsheet. when I enter this months bill, I have formulas in it to automatically calculate if we used more or less energy than the previous month and the previous year.
Medical expenses: a couple of years
***I just thought of something!!! I wish I had kept all my bills for the cellphone because it lists what you're paying for. sometimes they change what's offered and try to charge you for something you're supposed to have for free... like picture mail, texting, etc. that monthly bill is your proof of what you signed up for.
I probably keep more than I need. Actually, I know I do!
When in doubt, take a picture of it and save the picture.
Good luck! ~C.~