I was under the impression that US TV had about 30 seconds every 5 minutes or so? So you end up with about 6 ad breaks in a half hour slot. 3-4 minutes every quarter of an hour is the typical in the UK, and yes I agree that DVRs have killed it. As an interesting side note, it's hilarious when watching live television to watch my dad pick up the remote at the ad break, attempt to fast forward it, and look confused when it doesn't work.
