To throw in my two cents
2nd chances yes, 3rd+ chances no. If you made it clear that the 2nd chance was dependant on them changing their behavior with you and they don't manage to do it, then they will NEVER do it.
But also, even for second chances, only if you actually want the friendship and get something out of it. Don't feel like you have to be friends with someone because you "feel bad for them", if that friendship is nothing but a drain on you.