Are your legs tired after climbing a long couloir?

[mall walker]

for me, a lot of the "it depends" for me has been based on things like how much rest i've had, the company i'm keeping, adjustments to altitude, and the hairiness of my palms

beating off is my preseason training regimen also

[detrusor]

Have to be sure and switch it up so both arms are strong

[GeezerSteve]

Booting or skinning up uses a large muscle group, aerobic if you're in decent aerobic shape and doing it right (e.g., keeping HR within MAF), so the limit is O2, not muscle fatigue (except maybe late in a big 7,000'+ vert day when muscles can get damaged by late in the day). Compare running a 10K or half marathon foot race, where aerobic function is the limiting factor, not tired legs. Late in a huge touring day can be more like a 50K ultramarathon, where muscle damage late in the race can trump aerobic conditioning as the limiting factor.

Booting/skinning muscle group is also a different muscle group than skiing down.

Throw in an overnight pack or extended stretches of frontpointing and the equation changes because stabilizing muscles can fatigue at a faster rate.