You can set time limits for each application individually or group applications together by type (such as "Games"). Therefore, it does not make a difference how much time the user has spent on a particular game, rather; the total time spent gaming.
Each child can have separate limitations. For example: if you want to restrict the youngest child to 1 hour of games per day and your teenager to 4 hours this is possible. These limitations are customizable for daily, weekly or even monthly usage scenarios. Once the time limit has been reached, they will no longer have access to that application, or group of applications. Also, the termination of a program is done in an elegant manor. Visual and auditory alerts are given well before applications are terminated, allowing the user to save their game/work.