I agree with Jim. It is in a BIG pot already. These like to be root bound. The only thing I would worry about is the roots rotting, but you seem to be keeping it happy. I see what looks like potting soil or very fine bark as the medium.
The main thing you want to watch out for:
Don't overwater - you seem to be doing fine. It looks happy and the leaves look very good.
If the leaves start to wither or wilt - check the medium. It may need to be refreshed, because it does break down.
If you decide to repot, check the roots and if any are black trim them away with sterile scissors (use a 10% bleach solution or a flame).
Check for slugs or snails.
Clean your pot (or resize to a different pot - depends on the root size).
Put fresh medium (if you have success with what you are using, don't change). The plant will be happy in the same type of mixture. Change it and the plant will take a setback to get used to it.
Make sure you clip it firmly in the pot using rhizome clips. Here are some links that will help you out in general.
http://www.aos.org/Default.asp...
http://www.aos.org/Default.asp...
http://www.repotme.com/orchid-...
