There's no constant for me. It depends on the style and how long it lasts. I've got some boot cut jeans which are on the verge or a flair, and I haven't thrown them away.
really depends on the clothes. I have some which as soon as they start lookign nasty go, and some (ie my gf ferre shoes, my vintage bally's) which i will gladly get repaired every few months so i can wear them forever! Classics such as a great cut pair of black pants, or a leather jacket, i will keep, while seasonal items that were cheap to start of with will be gone quickly. depends a bit on how much of an investment the item was ;)