I don't think 'immortal player' is such a good idea, However I'd like to see players careers last longer in teams than they already are. The youngest players are 18 year olds and they are "old men" for training sakes when they reach the age of 26 and by the time they are 30 years old, they are finished basically, quite sad to see important players and players that perform amazing decline within months of purchasing them. If with a push with lots of power training, a player can only remain realistically in your team for a calender year at a good enough standard to remain in your team.