The owner doesn't pocket the extra cap money, it just rolls to the next season. Woody wouldn't blink an eye to spend to the max if it meant having a winner. He has a lot of faults, but being cheap with player spending isn't one of them.
There is never a good time to waste money. You will always be robbing your future team. $5 million not saved this year will be $5 million we won't have later when we (hopefully) need it to make a run.