It wasn't that long ago that a 136" track was a Long Track. My 95 Summit has a 135.8" (yeah yeah), with a 1 1/4" paddle. That was considered an awesome mountain sled back in the day.
It also depends on the rider. A young kid was driving around on a 92 Indy Sport with a 440 fan and everyone who watched him climb up and down these mountains wanted to know what he was riding. The key with him was he was 14 years old and weighed 85 lbs soaking wet.
A few years later he was riding with the Slednecks. I'm not sure he was an official Sledneck rider, but he was always riding right along with them.
I now ride a '15 Gade with a 137" track, 1.75" paddles and took it to the mountains this past winter with no problems going where I wanted to go.
I rode with a guy that had the Summit 174" and he said he was going to sell it and get something shorter. He said it was great for pointing it up a mountain and going to the top, but other than that it was just to much track.