Yeah, I guess you're right - the debts are probably long gone. However, on this site we generally only deal with the legal and economic side of things; nevertheless, there is a deeper and perduring moral aspect to our actions also.
While legally, the enforcability of a debt may last only x number of years, morally, it may well last forever, depending on the circumstances of the case and the resources of the lender. (valid and honestly declared bankruptcies excepted). So if the man whose conscience is in as an INFORMED state as he can put it concludes that he still morally owes the money and has the wherewithall to pay it, it's beyond the scope or mandate of this forum to dissuade him.
Still, if he decides to proceed, there's nothing preventing him from trying to negotiate a reduced settlement from past lenders; something they may be amenable to given the age of the debts and the fact that the creditors have of necessity written them off by now. As well, he doesn't have to tip his hand to the lenders before negotiating that he has a new found source of wealth.
Ray