There's no official policy (like some boards)... if it's appropriate to the topic, and the persons involved are still active on the forum, and it's not been TOO long, I'd say "go for it"
OTOH, for the most part, there aren't a lot of "Use the search" posts on here, unless it's an extremely common question that is asked all the time.
Unless the latter is the case, it's probably not going to hurt to start a new thread.
We do get more "comments" about necro-threads than "use the search", but again, if it's a thread that would remain productive if reopened, it's fine.
We've got a good group here.