User blog comment:B214/Volume 22 spoilers/@comment-29778526-20170126060633/@comment-9595671-20170127071539

B214: I agree, plus when Issei's lifespan decreased, I don't think it was stated Issei had exactly 100 years left, but that he had 100 left. When he was a human, Issei was 17, so he'd die at 117 years. If you multiplied that by 100, then that's about nearly 12,000 years.

I'm not if another thousand or two could happen, but a few hundreds of years past 10,000 could work, with anything near another 1000 being rare. Going by your additional 100-200 years, Issei's friends would live long enough to see them again if Trihexa isn't dealt with before then because they're all around Issei's age.

Plus I think in Volume 21, when Vali talks to Issei, he mentions that he'd be able to live long enough too. I don't think having Albion increases his lifespan the way Issei's may have been due to his new body, so he likely knows he's got enough years to see Azazel again.