I regularly see various interesting, but old (unanswered)questions in the 'Similar Questions' box. Sometimes I could add a useful contribution and I'd like to answer them, but I'm hesitating because they've been asked a long time ago. OP might have already solved the problem, or he's not even thinking or caring about it anymore. To re-activate the question would be unnecessary for him(or her). On the other side, it still can be of value for users that come across it and have the same question. So I'm in doubt, what do you guys say is the 'limit'? a week? 1 month? 3 months?
Of course it depends on the question. If it's very personal there's no need to put in any effort after months, but a general question about principles can still be susceptible for an answer. It's not always easy to determine if a question is general or personal though. Any suggestions?
NB. This question is similar but different from this question.