Since the Survivor Requests have been introduced, I would receive them once every two days. There are a variety of them available, or so I've heard: collect X amount of a single resource, kill X amount of Infected, raise a survivor's XP by X, etc.
During my trudge to level 50, I'd only ever received the "Raise this Survivor's XP by X" requests, that carried the reward of a substantial morale increase. Once all of my survivors reached max level however, I started receiving the "kill X amount of Infected" for a reward of several thousand XP. At this point in the game, the XP is a completely worthless reward.
Is it possible to receive morale bonus rewards for Survivor Requests at level 50?