Setting Session Length When User Logs In

From a previous question of mine I found out I can set:

session :session_expires => + 10.years

In the application controller. But I want to be able to set the
session_expires when the person logs in based on if they click ‘keep
me logged in’ or not. Does anyone know how I could do this. I can’t
seem to find any good information on this but it should be very
simple… in theory.

John K. - where software engineering knowledge gets indexed - software engineering conference