I've been in game sessions ranging from 3 hours to 8. But I don't play WoW or any other MMO. How long do raids tend to last? I have a sense you can play a short raid in less than half an hour. I'm looking for the differences in what appeals for MMOs vs. tabletop RPGs, so I can play to the strengths of face-to-face gaming, and not try to compete with multi-million dollar technology.
I used to play Everquest... for several years. Everquest was all about getting equipment from raiding (at least at first). Later, it became about getting faction (to be able to get better equipment). Raids would take anywhere from a few hours (mostly coordination and buffing time) to a weekend (Temple of Veeshan - complex tactics, zone entirely full of dragons) to accomplish, and it was mostly about figuring out the best tactics and mix of roles to handle the situation. It took me 6 years to realize that I was just a hamster on a wheel, grinding up experience and factions so that I could get the next big item on the list.
When WoW came out, I beta tested it but never bought it... initially. Instead of buying that I moved to Neverwinter Nights... with tons of content and a DM client I ran a campaign in that for a couple years. Then my neice told me about the roleplay WoW server, which sounded appealing. I played it for a bit but found that it was very similar to Everquest... it all came down to gear. The story in WoW really is great, if you stop to play through it and read everything... tons of story. I was getting sucked into my hunter's character but then starting finding out that I wasn't effective on raids, mainly because of my stuff. So I stopped playing WoW too. There are shorter raids in WoW, things that only take a half hour to clear but the motiviation for them isn't really story driven, and not what I was looking for.
Now, it's Dragon Age, very immersive, not at all about the fight, or the stuff... the story. I wish it was multi-player and I wish it had a DM client, I would drop tabletop for that in a heartbeat. So if you were looking for something to bring to the table, take a look at Dragon Age... there are story reasons the combats happen, not that they just happen.
If you were looking for aspects that appeal the MMORPG players, I would say to use more environmental things that affect the combat: For example, I had this idea for a fight in a wind tunnel against Belkers, where you could, as a minor action, make acrobatics or atheletic checks to control your movement rate up or down, and your weight actually factored into the fight (too light, you go up, too heavy, you go down). I can recall a number of fights where the environment played a role in the combat: Fight in an acid pit against a black dragon, or fighting on floating rocks (don't fall off!). I would also add in unexpected things. Have a trigger point set up at 1/2 hit points to have something happen, again at 1/4.