Are there times to pre-empt with a "strong" six trumps in bridge?
Under most circumstances, I wouldn't. If your partner has 3 or 4 clubs and mediocre strength, and decides to support, you might find yourself in a disastrous 4CX or 5CX while your opponents didn't have anything better than a game.

It depends on your distribution as well. With 6-4-3-0 I might feel bold enough to try it. With 6-3-2-2, probably not.