I went down to a 165 last year as part of my overall transition from dieseling along at ~70 RPM for years to the mid 90's. I saw no need to swap gears for my typical rides which is a compact and 11-34. I do now change gears a LOT more than I ever did before. Strange how much comfortable RPM range I lost in the down size. I couldn't imagine a 155, I'd probably have to change gears for every 0.2 mph 😁
I'm keeping 175 on my MTB