I don't have kids that age but was very into technology at that age. I was allowed to self-regulate some days lots of hours some none - the timer thing I can see being seriously annoying, and probably make you keener to get on it if you know are so restricted. I would ask him what he thinks are reasonable limits and accept them or get him to compromise half way with you. 8:00 sounds kind of early to me, I never had a bedtime so would go to bed according to how tired was sometimes early sometimes late - is prob a good skill to learn determining when to go to bed. I read an article recently about technology vs TV and technology was preferable over TV and the impact of technology on activity levels was interesting in that taking away technology didn't increase activity levels.
I think the bedtime works, 95% of the time he's asleep when his head hits the pillow and is awake and alert at a reasonable hour in the morning. Friday and Saturday nights its usually 9.30 bedtime. I don't see a point in him staying up later for the sake of staying up later.

We also limit tv, I would much rather take them to the park, go for a walk or encourage them to do something else.