I am ready flip the switch for My Domain, and click Deploy to Users.  I've tested the new name, and I can login to the org using the new domain.  But I am concerned after reading some other posts.  I have seen that Users might be locked out for up to 24 hours when I Deploy to Users?  I'll turn it on over the Labor Day weekend.  I plan to leave access to the old instance based domain enabled for a while.  TIA!