This one is slightly different from the other shrine reward categories. Unlike the other rewards for score or xp where you are spending the xp or need to have a certain score, the age based rewards need you to be under that age to access it. As long as you are under the age limit you can access the reward whenever you want, but obviously this can be done at the very first statue that you come across in the first Hideout. The highest benefit has a limit of 25 and under, next highest is 40 and under, and the easiest one is 60 and under, but you can immediately go to the highest benefit if you have access to it.