I think it depends on the context of the reviving post... if it's in answer to a 6 year old question and it's pretty obvious that the poster didn't realize the the OP wasn't current, then I don't think there's anything wrong with a gentle
reminder to check the dates of posts before responding. Another good indicator is the ratio of views to responses. A post with 600 views and 2 responses is likely long out of date.
But there's nothing wrong with "bumping" an old post to revive the discussion or to add something relevant. As Shack indicated, sometimes not doing so will produce a suggestion to search old topics before starting a new thread
Can't win sometimes.