Many years ago I did OSL-LHR-JFK-LAX-HNL-LAX-LAS-MIA-SJU-MIA-LAS-LAX-HNL-LAX-LAS-MIA-SJU-MIA-LAS-LAX-HNL-LAX-LAS-MIA-SJU-MIA-LAS-LAX-HNL-LAX-JFK-LHR-OSL in 10 days or so, including three immediate turnarounds in HNL. Was an interesting experience, honestly not too bad except for a slightly sore back towards the end after too many hours in terrible AA 757 seats. I had two nice rest days, one in HNL and one in SJU, which definitely helped a lot.