With a DVR you don't have to watch the commercials or watch it at any particular time, you just have to set it to record.
In the "old days" of 20 years ago, TV shows had 15 mins of commercials per hour. Half hour shows had 7 or so.
The hour shows had breaks at the 15 min marks, so you had 4 acts. As time has progressed, shows have shrunk to 43, 42, and now roughly 41 minutes. However, at the same time the networks didn't want those breaks to be too long, so they switched to having 5 acts, an extra commercial break per hour. Half hour shows are now 21 mins if you're lucky.
Of course, go back and watch TV episodes from the early 80s or before and you'll notice they're 51 minutes! Not just the original Star Trek, but as late as the first couple of seasons of Moonlighting.
The Jedi Master