Probably about that. Ret is a decent leveling spec until 30 or so, after that Prot will actually allow you to last longer, take on more enemies at once, and basically survive what would kill most other players. I haven't leveled as Ret in a bit, so it's entirely possible that it's still very good.
I think 2-4 weeks is a pretty decent figure; you'll save on corpse runs and close calls, but your damage won't be amazing, so it balances out.
I think 2-4 weeks is a pretty decent figure; you'll save on corpse runs and close calls, but your damage won't be amazing, so it balances out.