So basically, advanced warning will not always be given, but if you are lucky you get a little warning. So you always have to be ready for that one second grace period
How's this for a theory - If you check your reaction time (plenty of apps about eg
Sheep Reaction Test Game) you will find most people can react in about 1/4 of a second.
So that means you probably have about 4 times as long as you need!
PS. I got Ave - 0.2766