I bought my cvt in feb. in northern ON and you can see my fuel econ numbers in the log.
The CVT requires very little warm up, I get dressed, run out and start the car, come back in and put my work boots on then go. Not much more than 2 min warm up.
I drive slowly (no more than 2000 rpm) until cold light goes off (about 2 min) then off to the races...
Winter mileage is closer to 50mpg than the 64mpg rating but entirely acceptable.
Side note.. the cvt loves cold temps and this car is outstanding in the snow.