Hi bud, what your doing is th safe option, but I find assigning skill to the players strengths is better!, e.g. if you have a player with an SA say dribble or freekick, then give him stamina and attacking! or assign attacking and condition to attacking player like midfield and strikers!, for defenders and defencive midfield player assign to defence!, I only keep players a few seasons so as long as you dont let a players skill sets range get two far apart( 7-10 )points difference your be ok!, as soon as you see a players performance drop badly then start evening out the other sets.