I agree with Bob here on the frezzer time and how to achieve it, that said given the method you should be okay in the frezzer for about 2 to 3 years before any burn damage can occur.
The other method would be to cape the deer and turn, flesh and salt the cape. Dry and store in a cool dry place and assure no moth or bug problems and it should be mountable for 5 years plus.
Proper salting is the double salt method using new salt the second time to assure all liquid is expelled and complete penetration of the brine has occured.
I once forgot a Wilson Snipe in the frezzer for 15 years. Very delicate to skin but the mount came out awesome. I would show the picture of it but 6 months after I did it the dog got into it and it is but a memory now.
You would be amazed at what a good taxidermit can do with older mounts.
Note: the grip in my Avatar was done by Bob at Git-A-Grip:thumbs_up
2C