Here is my two cents on the topic of warehousing players:
Some people can and do play lengthy careers. I managed to play for over twenty years in minor (really, really minor) league hockey. I played fewer and fewer games as I aged, but I was always on the team and ready to go.
I can think of several professional players who have done the same in their careers; Chris Chelios comes to mind immediately. He has rarely played full schedules with any team over the past few years, but was available for the playoffs if needed.
As for my team in the SIM: I do not warehouse players to preserve their careers, or to improve their ratings, but to limit the number of graduations I have in any given season. I do have one player who has been with me since year one, but one of the main reasons he has been warehoused is that he is better than any rookie I could pick up as a injury fill-in player; but he has rarely given me the stats I wanted to see to be allowed to play in an entire season. He did play in 4 of 6 playoff games last season, but he scored a total of 1 goal, had no assists and was a -2 for the series.