I've always wondered about that, the morale issue, no way to know really, some players play well and play badly almost without rhythm or reason, I have only had one player make it with my team for 4 seasons, only one. I have 7 players ending their contract this year, from experience maybe 2 will be signed for the next 3 years, the rest will be traded away before long, but that is just me.
I would not sign anyone until very late this season. I say make them work for their money!