I only decide my squad in the third day, because thats whend you see your opponents in league.
Also i prefere only to start Buying on 3rd day, since most people already spend there money, and you can buy there fast trainers more easily.
I prefere to sell the players i know i will not need in the last day of season, since there price is on maximum, and not every player generate a bid war.
Players with 33 years old lose a bit of MV whend turn to 34, but it is very insignificante.