Mileage, mileage, mileage. That was the answer for my son at least. He erg’d long distances at steady-state A LOT. He only did 2K’s once per month–his normal daily routine was much more mileage than a 2K. I remember numerous times he would come in from the garage (where our erg was) and say that he had just erg’d 20K. He would do that in 5K pieces with a brief rest in between pieces, but it was in one overall session. He was an erg maniac, but that’s what it takes I think to drop your time. It didn’t hurt that he was a very fit athlete before ever having become a rower, having been a competitive wrestler. He was accustomed to the idea that to excel in your sport you need to do lots of training outside your actual sport. I’m not a coach so take what I say more as an observant dad, but I just think the difference was how much steady-state mileage he did on the erg itself.