That's one way of looking at it.  the other way is...  No one knows how long it's gonna be before we find a block.  So I'm going to set my miners and forget them for the best average payout on all blocks.


Because you can say that miners aren't contributing for the first hour of a block, or you could say they are helping to find the block in less than a hour.  It's all relative, math, averages, etc.  Play the averages, it's your best bet.