does creditors fall off after seven years?

what i mean is my credit is shot the only thing that is a constant are my student loans... i have three or four credit cards that did not have no more than a 500 dollar credit limit but i defaulted on all of them ( younger and dumber ) but it has been at least five years on all of them. but i am getting letters from debt collectors on these old debts saying that they want to settle. but i was under the impression that once seven years pass you are free and clear should i settle or what?