I delete them. I figure what's the point? I have enough on my DVR that's not cancelled that I can use my time to catch up on.
One exception I made this year was Surviving Jack. But I figure that's a show that's not going to leave on a cliffhanger so there's not much to get invested in and feel like you didn't get the closure.
Looking at the line up of fall shows, none really peak my interest. I had a lot of my favorites that were renewed for next season, so that'll give me enough TV to watch.