Reward schedule is an reward system this is based on a time schedule, This is where the player is reward for spending some time on quest or for completing a quest.
There is two types of Reward Schedules.
What does Fixed intervals mean ?
Fixed Intervals refers to a schedule that is on fixed time (say you play a game for 60 minutes and you get rewarded XP, or when you collect something from hitting a tree you that you are rewarded with a peace of wood.
This tends to create a low engagement to the play to play more or collect more to get his/her reward from in game.
What does Fixed action mean?
Fixed Action Rewards, Players complete a certain task to receive an reward that they was expecting. Also if a player Buys a Sword from the in game market place using the game currency they can be rewarded a free sword or some in game currency back.
The picture above shows an exact example on what I was talking about. You can earn game deals if you complete or get a good score in game.
If i was to implant this in my game I would Make the reward system fixed Intervals, This would give the player satisfaction of completing a quest.
If you want to lean more about visit here