A longer season would be good, as you get to train your player to a higher level every season. Four weeks is the 'sweet spot' where most players gain about 20% only to lose it. I know this is the same for everyone going up, but you feel like you're running just to keep still. IRL players up their game when going into a more competitive league.
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If the seasons becomes 6 weeks for example I can guarantee you that the player will either lose more quality 30%, or they will grow slower.