I have a pair of shoes (Mad Rock Drone HV) that I got resoled 3 times already.

Usually the people who resole it tell us when we should move on to a new shoe, which is when the old shoes cannot be resoled anymore, but they have yet to do so for mine!

I have friends who have resoled theirs just twice and were told that there probably wont be a next time, that their shoes are just too damaged overall.

It really depends on your shoes and the status of them. If areas of the shoes are damaged that are not going to be replaced or fixed in the resole, then resoling obviously wont help them. As for the amount of time a climbing shoes can be resoled though, as I mentioned, mine have gone for 3 resoles, and will probably go fro at least one more, my friends have gone for just 2 and will probably not go for any more, so, it depends.

Try to send them as much as you can I would say.