Another tip:
Sometimes, when you're replying to a topic, there's this text that appears:
Warning: this topic has not been posted in for at least 90 days.
Unless you're sure you want to reply, please consider starting a new topic.
(This won't appear if you have Quick Reply enabled. If you use that instead, then be observant in post dates)
That message up there, of course, implies that the topic is old. Now, depending on what information you bring to the topic would make this warning completely null or not (i.e. if you post something that has value in information, then that's okay).
If you're asking for a request dependent on the OP, then ask yourself and do this before you post:
1) Has this user been active in the past week?
2) Check the post dates once more.
But I think you got the gist of it now. ^^