USA to Tahiti would be about 7 or 8 hours. It's another 5 or so on to Auckland. I've done that routing and agree that you need to stop in Tahiti for at least 4 nights to make that worthwhile.

I would also encourage you to spend as little time on Tahiti as possible and head to Moorea (or Huahine/Bora Bora if your pockets are deeper). Tahiti's nice, but it's got nothing on the other islands.