Possibly the Companions could be completed in one really long session, perhaps depending on your combat difficulty settings. (I'm playing on Master, with some mods, so I die a lot and it takes longer to complete dungeons, etc.) I did Companions, Stormcloaks and Main Quest, plus a few daedric quests and collected about 8 or 9 shouts, all with one character and that took about 150hours.
However, my first character I played 200 hours and barely completed about 70% of the Thieves Guild (last thing I did was get the Eyes of the Falmer). Didn't join any other factions, did just the very beginning of the MQ, only collected a few shouts and did about 2 or 3 daedric artifact quests.
My third character was a mage, focusing solely on the College of Winterhold. I played roughly 170 hours and only completed (I'm guessing) around 60% of the College of Winterhold. Also didn't join any other factions, didn't do any daedric quests, and collected only about five or six shouts. Only did the main quest up to Kynesgrove.
After doing the first Mage's College quest at the archeological site, and in between each of the major steps of the main College questline, I collected books and Shalidor's research for Ugag Gro-Shub, and helped with a lot of other smaller quests around the College, helping J'zargo, Ommund and Brelyna, etc. These smaller quests altogether took around 170 hours, and then before going after the Staff of Magnus, I decided to start over with a new playthrough in order to try some new mods.



You can at least give me a free tavern outfit... 