Besides myself there are very few I actually CAN listen to for hours. Re: me, I have no choice... and re: others, they really need to be capable of a lot of different styles and originality to keep me from pulling my hair out. All through college, as a deadhead, I listed to the Gospel of Jerry from dawn to dusk (and usually well beyond) without ever growing tired of it. At the time I wasn't in to Peter Green and Duane Allman (the other 2 on my current list) and while I listened to them, the spark just never lit. Once it did, the fire has been inextinguishable. The others, although magnificent players, start to grate on my after awhile as their bag of tricks isn't as deep as it needs to be to maintain my attention... and so my mind... starts... to...
There are plenty of guys that can stretch a solo out for 20 min and keep it musical, and interesting without sounding like they are just rambling aimlessly. But to listen to for hours I would go with
Lately I have been checking out Eric Johnson and Steve Stevens. Two totally different playing styles but I like them both. I like many different guitar players I think you can learn something from all if you keep an open mind.