That whole unpredictable thing is somewhat in your head. By January 1st last year I had 8-10 days at Blue which covers the cost of a full pass. January had quite a few great Sat and Sun mornings of 10+ cm snow falls.
Last season which was one of the mildest winters on record, I had 100+ days of boarding (30 or so was out west, rest was in Ontario). I loved every minute of it.
Anyway, double downs are still a great option!
I agree that there's little risk of not getting your money's worth at Blue Mountain, over a season they are great at making snow. I was at blue last year from Xmas to New Year's and there was lots of good riding to be had but it was a bit of a fluke. As I recall it was looking iffy int he days prior to Xmas, (only about 3 runs open with ribbons of man made snow) when luckily they got a big dump of snow on either Xmas day or Boxing day, after which pertty much all runs were open shortly after.
Hopefully it's a little colder in December this year.