I will take a completed model to each contest - once. Win or lose. If it takes me three years to get to a particular contest, I will bring some older stuff.
The guys that bring the same stuff over and over, are usually the same guys that go whining to the contest judges/promoters to find out why their model didn't win. I've even been to a contest where the judges saw the builds and said, "This one again, he's won in the past, ignore it, whats next?" Is it right to do so? Probably not, but I certainly understand the sentiment.