[NTLUG:Discuss] Can Linux help me limit my kids' time on the computer?

[Lance Simmons]

I want to limit my kids' time on the household computers.  Well, just
one of my kids, really.  I'd like to be able to allow him a certain
number of hours each week, and somehow automate the restrictions.

Is there a way to put in place a policy that says "you've got ten
hours to use this week, any time you want, but after those ten hours
are finished, you have to wait until next week"?

In any case, even if there's not an effective way to automate such
restrictions, is there an easy way for me to keep track of total
number of hours logged by a particular person?
-- 
Lance Simmons