Q: When should I respec to Prot?

A: Level 10.

I've been Prot since my first point and I wouldn't change a thing if I had it to do all over again. This is perhaps the funnest spec on any toon I've played. I leveled from 35-38 today on the murlocs in Dustwallow in almost one continuous pull. I've leveled 4 other toons to 70 -Mage/Warlock/Shaman/Hunter- and this is without a doubt the most fun I've had yet.