Do you use a bag until you're tired of it?
I used to, but I found myself getting too bored with the bag(s) I bought. So, now, I usually buy one statement bag (or a bag I reallllllllly want) and one or two I like a lot. So, I can rotate them.
Do you use it until you want another one and one of your bags has to go for more room and/or money?
As I said, I try to get about three bags at about the same time. I usually use one bag for a week to a month then switch to to the second for a while than the third. No, I've never sold a bag I've bought myself. I only got rid of one bag someone give, because I was never keen on the brand and style and didn't enjoy the quality. Usually, I'll buy one bag full price and try to find the others on sale or on ebay from a good reseller. So, that way, it's more like I paid for 1 or 2 bags instead of the 2 or 3 I actually bought.
Do you use it until it wears out? If so, what do you consider to worn out, i.e. just worn corners and bottom and cracking in handles or until it looks like it's been on a long and treacherous journey with Indiana Jones?
All three above?
Since I rotate and clean my bags often, even the preowned ones, my bags tend to look good. This isn't really an issue for me. To me worn out is just a state where you can tell it's been loved to death. Like the leather is extremely faded or scracthed a lot. Something major. However, some minor wear or nicks can give character, but past a certain point is too much. Never been here yet, but I would retire or get rid of a bag if it were so worn beyond repair that I couldn't take it back to the store and get it reconditioned, or whatever they they call it.