For 8-12 hour comfort, I'd think a more traditional over-the-head design (like the Sanyo PorkRind described) would make more sense than an in-the-ear design. Maybe something like these:

http://www.amazon.com/dp/B00007M1TZ
http://www.amazon.com/dp/B00001W0ET
http://www.amazon.com/dp/B000E1HVGQ

You might want to check out the Etymotic headset, though:

http://www.amazon.com/dp/B0001YX9ZI/

It has the best audio quality of any headset I've ever used, and works very well even in loud environments. With the smaller windscreen on it, I find I am able to hold a conversation while walking through Times Square (something I do a lot), whereas my previous earbud-with-a-mic-on-the-wire headset was virtually useless in that environment.

I'm not sure, however, if it would be comfortable for 8-12 hour stretches, as I've rarely worn it for more than an hour or two at a time. And it may have some slippage issues like the Jabra. But it's worth considering.