As Mariner said, you can include backcountry skiing/alpine climbing in your training. Especially with the coming ski season, many people will incorporate backcountry skiing into their aerobic training for the week. The key is to stay within your target training volume for the week and have a gradual progression from one week to the next. If the training volume is erratic and/pr you have not fully recovered for the next day/week’s training, then training might not be optimal.
Regarding extending your training plan, review this forum topic –
Hope this is helpful.