If it’s already on the front page, then there’s no need for a bump. If you bump it after an hour, that too is no need. If it rolls back to say, page 2, then I would say it’s perfectly legit to bump.

Bumping too many times or bumping every, say, hour, is considered spam and pretty much annoying. If you were able to bump every 10 minutes, other people would do it too. That’s why ‘bumping’ is always used sparingly.