I think the evidence is not there to freeze hCG for later use without running the risk of decreasing effectiveness. Why take the chance for any decreased efficacy, especially since it is your BALLS.
It would be nice (and easy) to test what freezing would do to hCG bioactivity. And, the end point must be bioactivity and NOT immunoactivity. As it would be a simple clinical trial, maybe someone will take the time to run.
I think you're right, the evidence for freezing isn't there. I found a few more references in chem publications that seem to suggest it might be possible to freeze neutral buffered aqueous solutions of hCG or reconstituted hCG-beta for long term storage in single use aliquots at -20°C as you noted earlier, but they also recommend the addition of a carrier protein (0.1% HSA or BSA) as well as the avoidance of freeze-thaw cycles. The use of a carrier proteins and precise storage requirements doesn't seem at all practical for the home user.
As is usually the case, following the manufacturer's instructions is the best option, IMO. If your balls depend on it, it's really not worth the risk just for the sake of a few bucks saved.
CBS