Never had a winning answer - so not sure if I would use it again or not. But I guess if it where a "word or less" competition and you made it relevant to the company involved then it might be hard to re-use it again.
No, I try and think of something fresh and original each time, also they usually require completely different answers each time depending on the competition anyway, and I have done well in a few WOL comps over the years.