The tournaments that last some months will be difficult. For example, if it is 3 months long, the player that starts the tournament at 5 stars will be 3 stars at the end. Or the players that starts will be no longer in the team because you keep improving the squad, buying new 5 stars players every season.

Of course this is only a point of view, but it's a little unrealistic that you use new team every month of the tournament or something like 20+ different players.