Consider at age 43 that he has run a 1:02 flat half marathon, and also something like 27:45 10,000 at age 42.
So you have a guy that is still the second fastest 1500 meter runner ever, running 1:02 flat at age 43 for 13 miles. I suspect had he wanted to back in 2008 or so that he could have run in the 2:04 range for a marathon, which at the time is either a WR or very close.
A faster version of Mo Farah I guess.