The player will ask for what he thinks he can get on the open market; as players age, their ratings will decline, so you might want to be cautious extending older player's contracts too long. In my experience I haven't had this happen, but unless you're really loading up the bonus or are signing lots of older players, it shouldn't be crippling. I'd be curious to know who asked for a 5-year contract and then retired right away, 5-year contracts should only be requested by players with a pretty high rating which in theory should decline before they retire. But, this is part of the risk of signing older players to long contracts or high bonuses.