I just found something that might be helpful for you. This Q&A is from the UCLA website:
Sep 10 2007 03:47PM
Q: If I take the GMAT more than once, will the Admissions Committee average the scores or take the highest one?
A: We will see all of your scores but will take your higher score if you take the test twice. If you take the GMAT more than twice, we consider all scores, but don’t average them.Based on all of your comments and school websites, I think most schools look at all your scores during the last 5 years but don't necessarily "average" them. I guess it is ok if your scores have improved over time. Is it safe to assume this? Please post a reply if you have seen other schools who take the "average" if taken more than once.
Thank you everyone!