Since around 15 years ago, and I seem to recall it came out of either a safety forum related to the rejected takeoff issue or it was from Flight Safety Foundation, it was RECOMMENDED to actually utter the word VEE- ONE at the computed V1 minus 5 knots.This is very good practice and should be applied everywhere.The reasoning is the V1 does not change at all, however the words VEE ONE will be stated by the PM just prior to V1 thus allowing the pilot in the left seat to make his go/no go decision at or before, but not later.Many many times in the simulator I have seen pilots try to reject just slightly after V1 and while most of the time with long runways you get away with this but in the most limiting cases you run the serious risk of an over run/crash.
I am aware of many airlines having this technique in their SOPs but everybody should apply this.Its safer.