I've mounted deer capes that were in the deep freeze for 5 plus years. As long as they are wrapped up tight you should be fine. I use a big a roll of packaging film (saran wrap) and roll the thawed cape up and then wrap up tight in the film, then put it in the freezer. It keeps the air out and keeps the skin from drying out.
I found a cape in the bottom of my deep freeze a few years ago that was 14 years old, and in a garbage bag with holes. There were a few freezer burned spots but I had a set of antlers that would fit so I figured I'd try. Taxidermy supply companies sell a fabulous product called Stop Rot. I brushed it on and let it soak in. It actually even softened up the freezer burned spots. Mounted up great - not one hair slipped.
Not that this helps you now, but in the future if you have a hide that you won't be able to mount for a while you could 1. have it fleshed and salted in which case it would last forever or 2. vaccume seal it and then put it in the freezer.