I consider myself somewhat an expert on delayed ejaculation, since I have been struggling with it for 2 years now. It is naturally related to long refractory time because reaching ejaculation becomes more difficult with each "round" of intercourse. This is true for all guys I think.
The good news is that rebooting helps delayed ejaculation. My orgasms were almost completely absent before my reboot, but now after many long streaks I can quite reliably do 1 session of intercourse per day and finish every time. As for refractory time, I usually need 12 hours. Like you Zen, I can't usually do round 2 within the same evening. Porn was related to my problem, because when I tested my refractory time 2 years ago with porn, I could PMO 4 times within a couple of hours. I am still hoping that by continuing my reboot, I can achieve this kind of refractory time also in sex.
But even though porn addiction may be one cause to DE and long refractory time, there are certainly many variables at play here, as Gabe said. Some of them may be physical. For instance, my tight circumcision has reduced my sensitivity quite a bit (I can tell because the operation was done in my 20's), and it makes me more vulnerable to dysfunctions.