what, last remaining wild salmon run? really? what is that salmon run that runs up the copper river? are you saying that that is not a wild salmon run? 

you are wrong, it will last year round when they getting fully developed. mining companies are not in the business of working part time. they will spend the money to develop the infrastructure necessary to mine all year, 24 hrs/day, 7 days/wk, 52 wks/yr. mines of this size do not play around. the only limiting factor that i can see will be energy, like the fort knox mine in fairbanks, they will be forced to utilize diesel equipment until they can get enough electricity to run electric, meaning smaller equipment. the big stuff is all electric. you are absolutely right one day they will be gone, but not in our lifetimes or our children's. 

some mines build their own power plants so they don't have to buy the local power, they generate their own.