Lemme think... 1996 then, 2008 now... ok, that's 12 years.
Back during my SYX 1900 days...
I'll admit that I was in flight, beat to death from being on leg 7 of 8 one day, and I asked the captain if I could take a 10 minute "combat nap" during his leg. So basically all he had to do is continue flying but take over my radio duties.
I was out about five minutes when I kept hearing Chicago center repeatedly call "Skyway XXXX, Chicago?"
I woke up and the skipper was asleep too. Daggummit!
The scary part is that we had no autopilot.
The GOOD part is that the 1900D is so silky smooth and stable, that we weren't more than 20 or 30 feet off of our altitude and still on course.