So yeah when I first got the 598's the bass seemed flabby and uncontrolled, hiding the detail. With about 60 to 70h of loud pink noise the bass became controlled and now the 595's seem too cold. The detail came out and now they even seem more detailed than the 595's. I also did a blind test on my gf and she instantly didn't like the 598's compared to the 595's when they were new, a few days later and she preferred the 598's (not by a huge amount, but it was a hard decision this time, not an instant one like before), same music, same volume different burn-in; and she didn't listen to either set of headphones in between to 'burn-in' hear brain to them!
"Well 25h of running them they sound a little closer... Still the 595's seem clearer."
"So interestingly I now love the 598's after 70h of heavy burn-in they sound better than the 595's."