That makes no sense. The games don't get harder as the level goes up, why should the rewards? The way it is rewards in a good way. Early in training, it costs little and takes little time to level a pet. As they go up is costs a little more and takes more time. Much more like real training in anything.
It doesn't work that way. KingIsle put the maximum experience your pet can learn in one game at four experience points, unless you play from Grub Guardian, where the experience may vary. Hope this helps.
Charles Nightsword, Level 37 See you in the Spiral (or not)