I'm a little confused on the RSTP convergence process.
When I first learned RSTP, I learned that RSTP collapses the listening and learning into a single period of 15 seconds. Yesterday I read a whitepaper that said a switch immediately sets its designated ports to forwarding after receiving confirmation from the downstream switch that the best path to the root is through itself. If that's true it shouldn't take very long for the entire network to converge.
I don't have the link to that whitepaper right now. I'll post it when I find it.