Break-in time really depends on the boot.
I had a pair of Salomon Dialogue's that took me 5-6 days to break in, although there was nothing too sore in that time, just a bit snug around the ankles.
Then I got a pair of Burton Cartels this season, which had zero break in time. I was up at Whistler for almost 3 weeks, wore them new the first day, no problems at all.
By that time of year, probably a lot of the shops on the mountain there might be starting to run down a bit on stock, so there may not be a huge selection available.