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.
Depends on how they are wrapped up. The ears and face are the most susceptible to freezer burn so I always tuck them inside. The fringe areas of the cape will burn, but if you have plenty, it is not an issue. I've gotten heads that people just stuck in their freezer waiting to get it mounted without full caping and they have been freezer burned within 3 months around eyes, nose, and ears. Usually can re-hydrate if not to bad.
A tanned cape will last indefinitely in the freezer if it is hydrated before frozen and wrapped well in plastic and kept in a conventional freezer(non frost-free). A green cape that hasn't been spit and turned, in some cases even if it has, doesn't last very good over a year in my experience. Sealing them in plastic is crucial. If they have to be hydrated to be spilt and turned, those freeze-burned areas tend to slip in the tanning process.
Fleshed and salted hides do not last forever, maybe a year depending on where you keep them, as they are only temporarily preserved with a salt pickle and are prone to destruction and infestation, by various bugs, including the webbing clothes moth. You don't want those anywhere near your mounts, they are destructive.