There is no best age.  You should live your life in the present and enjoy it.  Not wait until you reach the age which you feel you may be at your 'best'. Live in the moment and celebrate life,  don' t worry too much about your future. 

Childhood ! The rest is just a slow and inevitable decay. As Latin poet said : Carpe Diem.

Every moment of your short life!!!! Enjoy it while you are  still alive....

it is best to live the moment and enjoy it. Every part of life has its own benefits , so you should have fun.