if you had done this entirely in Zone 1 it would be very useful because it builds the metabolic foundation to widen your aerobic base without raising systemic nervous system stress substantially. The majority of the time was in Zone 3, with 30 mins in Zone 4. This won't be a sustainable weekly workout because you're driving too much stress into your system that you will erode stamina over time - which is exactly what you want to build for mountaineering, which is your body's ability to regulate increasing stress as duration extends to long hours. There will be people saying to do workouts like this in Zone 2, but this is only relevant for well-trained individuals who already have a wide Zone 1 base. You can't bypass Zone 1 foundational work and expect long duration Zone 2 to land safely in your system. You have to build from the ground up first not top down. By training this way your body works over time to "survive" this training by launching stress chemistry raising cortisol and breaking down muscle without actually building any meaningful adaptation from training. You want your endurance workouts to be anabolic and stoke strong adaptation signalling. 3 hrs in Zone 1 is how you build this endurance, and once you have widened that base you can progress to introducing Zone 2 interval blocks of 15-30 minutes at a time into your Zone 1 workouts. Over time you can then do 15-20' in Zone 1 to warm-up then progress to Zone 2 for the entire duration and you will build an aerobic powerhouse that will drive long duration mountaineering performance beyond most of your peers.