M.K.
G.,
I also have two year old triplets that need to share the same room. I plan on having them in their cribs as long as possible. Of course at some point it becomes a question of safety, so we bought crib tents.
http://www.toysrus.com/product/index.jsp?productId=2404625
They have been a godsend, and I expect it will help keep them in the cribs for probably another year and a half. While others may look funny at keeping a kid in a crib that long, there are some issues that are specific to triplets that can warrant that. One kid jumping on a bed as they learn to transition, is different than one kid jumping on a bed that two others are sleeping in. I got the support and idea behind doing this from a local triplet yahoo group that we joined. I would strongly suggest you consider joining it. They have been a great source of information and support, not to mention triplet resales. This link should get you to the right place to join if you are interested - same to any other mom of triplets or quads in the area.
They are also a good source of information for what you can do in terms of when one wakes and the others sleep, and how you can handle that.
http://groups.yahoo.com/group/triplettree/join
Good Luck,
M.