Just checking to see what is preferred here.
Most people don't seem to give it that much thought.

As long as the subject line of an existing thread accurately reflects your question, I think you'll likely get a similar number of useful responses either way, since the default forum view sorts threads by last post date. Keep in mind, though, that resurrecting a truly necro thread may result in more posts about
that practice than answers to your actual question.
If you're specifically looking for the latest word on something discussed at length in an older thread, even resurrecting a really old thread seems logical and doesn't strike me as unreasonable. It's really no different and even a bit less confusing than starting a new thread with a link to the old one for reference, after all... But if you're posting a new question about a topic even though it's been discussed at length in general, a new thread is probably the least likely to result in off-topic posts. People (myself included<sigh>) have somewhat of a tendency to pointlessly, however inadvertently, reply to old posts in old threads that start up again, not realizing just how old the earlier posts are...