Finally tackled something I've been wanting to do for a few weeks now.
I took the 3 SPN episodes with the least amount of Sam & Dean and timed them. I wanted to know how little screen time the boys really had. Now the timings aren't exact, but I feel they're fairly accurate.
8x04 "Bitten" = 9 min 34 sec 9x20 "Bloodlines" = 9 min 2 sec 13x10 "Wayward Sisters" = 5 min 55 sec
Interesting how "Bitten" and "Bloodlines" have similar times, considering "Bloodlines" was the show's first spinoff attempt. And look how little screen times the boys had in "Wayward Sisters". However, what made it easier to deal with (IMO anyway) is that in WS we got to spend a lot of time with characters we already knew and were established. Whereas with "Bloodlines" we were given all new, unseen characters for most of the episode.
Anyway you look at it though...for most of these 3 episodes, the boys were barely there for those 42 minutes.