120 fork on a "hardcore" hardtail is too short IMO. I have a honzo that is supposed to run 120. When I got it I accidentally put a 140 on it (I thought it was a 120 but when I was measuring it in the process of replacing the fork realized what I had been riding). I set my DVO to 130 when I put it on and have found it shorter than I would like ever since.
On the other hand I suspect 180 would be too much to my liking. I think 140-160 is the sweet spot. Too short and it makes it difficult to carry speed when the going gets rough. Too long and you lose the fun of riding a hardtail.