SB 11.18.10
yas tv etat krcchratas cirnam
tapo nihsreyasam mahat
kamayalpiyase yuñjyad
balisah ko ’paras tatah
Translation:
One who with long endeavor executes this painful but exalted penance, which awards ultimate liberation, simply to achieve insignificant sense gratification must be considered the greatest fool.
Purport:
Although the process of vanaprastha described by Lord Krsna is so glorious that even the consolation prize is promotion to Maharloka, one who consciously performs this process for such promotion to heaven is certainly the greatest fool. The Lord does not want this process to be abused or exploited by materialistic rascals, for the ultimate goal is love of Godhead.