I wear jeans and denim skirts a lot, but these tend to last a long time because I don't put them in the dryer. When they do wear out -- i.e. when they develop holes -- I toss them.
Tee shirts follow a predictable downward trajectory. They start off as "first string", which means I wear them with a cute skirt when I want to look nice; as they get older they become "second string", where I wear them on regular ol' days where I have to go out to the grocery shop and pick up my kids, but nobody important is going to see me; then they become running shirts; and finally they get tossed in the bin.
Proper shirts (with collars) and knit tops (sweaters and lighter knits tops that are less casual than tees) are different. Often these last long enough that I either get tired of them or else they look hopelessly out of sync with my current wardrobe, but still have lots of wear left in them. In this case I donate them to charity.
ETA: rough timeline -- jeans tend to last five years, tee shirts one or two, and sweaters I'm not sure. I've barely worn them since I had kids, because I get too hot. I donated a whole bunch last year. Collared shirts last for flipping ever if you don't put them in the dryer.
I replace bras and underpants as the need arises, but I'd say a good bra lasts a year or two at most, even if I handwash. I only own four bras, so they get a lot of wear. Undies last longer.
