IME, 30-40 days reduces the potency considerably.
HOWEVER, experimentally, preloading pins and freezing them has worked with HCG, though potency decreases somewhat.
I have found no research, and only hearsay backing up this claim, but (having made a slightly different mistake with HCG at one point) tried it and found it to be better than the alternative.
If this is done, be aware to keep the pins in a sealed (preferably sterile) container, with the plunger pulled far back to allow the solution to expand upon freezing. Warm them in your hands before administration.
If others have tried this, no matter their findings, please chime in.