This is a waste!
I'll explain.
When you don't assign skill points during a whole season, and assign them when a new season appears, your team has a to high level (related to previous season) that assigning those points make not that difference in the new cup!

You'll have to do this 2-3 seasons with young players, not signing any skill points and keeping bad U-21 within your team in order to have an upper-hand on your opponent.
But this is a waste of 3 months of having fun while playing. Better get your hands on as many green boosters as possible and power train your squad during a whole season and then assign your points at the start of a new season.
Shorter time, more fun and a better value