I thought DISRUPTOR answered my question, but now with your post I don't know...
My question was indeed, is the acceleration boost itself variable?
And I thought DISRUPTOR answered that yes, it was. But maybe he meant what you described, which makes perfect sense, that if a time interval is available to get a fixed acceleration boost, the sooner in this interval you press the button, the better.
Now if the acceleration is variable, it could get different. If the boost start was better at the end of the time interval, pressing later might be better.
DISRUPTOR?