I wish I only bought leather bags, because I can't imagine leather bags ever needing to be retired. Leather can always be revived! Signature canvas/fabric bags, on the other hand, are another story. Too bad I think some bags just look better with a little bit of a pattern breaking up the monotone.
I've chucked some leather ones.
Because seams fell apart or color faded. Or hardware began gummy creeeeeeeeaking.
I blame manufacturers for those.

Chucked evening bag last year--noticed mysterious white paint spots on leather.
Happily, when insane hibachi chef tossed around fried egg pieces, replacement bag didn't grease stain (thank you, collonil).
I blame my mad lifestyle. And wicked fate.