Maintaining Access in the Router...

I want to know from everyone how to maintain the access in the router once hacked even if the owner of the router changes the password.

I brute forced the router login page and got into the router and i know the password, but i cant change it because the owner will be alert and i dont want to happen that.. So if in future the owner might change the password than i'll have to again do brute force which is needs too patience.. Is there any way to maintain the access even if the password is changed.

Like in facebook we all do once anyone's account is hacked we can change the recovery email and even the owner changes the password, through recovery email we can get into the account any time..

your help would be appreciated..