In the session scenario, I was talking about firewalls, not BGP routers (although, of course, you could have firewall features on a BGP router).

What I'm saying is, there are ways to validate and carry out network changes in a pretty robust way, including gradual rollout (if that's what you want) by using route or firewall rules priority or other mechanisms.

I keep being skeptical about this flapping strategy, but if this works in your setup, good for you.