Full Idea
Let no one delay the study of philosophy while young nor weary of it when old; for no one is either too young or too old for the health of the soul.
Gist of Idea
Begin philosophy when you are young, and keep going when you are old
Source
Epicurus (Letter to Menoeceus [c.291 BCE], 122)
Book Reference
Epicurus: 'The Epicurus Reader', ed/tr. Inwood,B. /Gerson,L. [Hackett 1994], p.28
A Reaction
I agree with this on both accounts. I think the correct age to begin the study of philosophy is four, and it is vital to continue its study up to the point where you can no longer remember your own name. 'Health of the soul' sounds right too.