I am 63 years old and just retired, so I have time.
I'm built like giraffe, 6'4" 200 lbs.
My winter routine is to hike with a 50lb pack in the hills, leaving my house,
and walking the neighborhood roads. I do that 2-3 days in a row,
then double the walking distance with no pack the next day.
Right now that's been at 20 below and packed snow.
I gradually increase distance with weighted pack and walking with no pack,
but I do not increase weight above 50lbs as endurance is most important for me. I take Sunday's off, and hike the other 6 days of the week.
As it gets above 0F, I cross-country ski on the days I am not backpacking.
I like packing with a weighted pack so I can fine-tune my 2 backpacks,
and I like the convenience of doing a loop right out of my house,
starting with a climb up to the top of the ridge and also a climb
at the end of my loop. I always pack and walk with treking poles.
The only weight lifting I do is logging for firewood and construction stuff
like 60lb blocks for retaining wall etc.
I do backpack camping trips scouting in sheep country after snow melts so that helps too...then twice a week works well for me. I think it's important to backpack where your feet and ankles get used to sidehilling, steep downs, and steep ups....that would be tough to do on stadium stairs especially the muscles used for sidehilling and toughening up the feet.