1: From 11am yesterday morning to 2am in the night, with the occassional bathroom and dinner break.

I'm eating breakfast now and once I'm done cleaning the cages of my animals I'm going right back in. ^-^
2: Yes, I ran into 2 non-quest dragons. The first one was just outside of... Riften I think. I was talking to the carriage guy for travel when all of the sudden the music changed and everyone started screaming. I looked up and saw this dragon circling overhead. With the help of the Riften guards - and a horse from the stables who wanted to help as well - we took it down, the guards were all amazed that they had seen a dragon and the horse survived and trotted back to the stables uninjured. Those Riften horses kick butt!
The second dragon I encountered near another city (don't remember which one, but it was in a forest). He appeared and circled around for a while, but because of the trees he couldn't land, or he simply couldn't see me because he flew away again without a fight after a minute or so.