I've noticed pretty much the same thing. Except I wouldn't even rate it for 21 days. At two weeks it seems pretty well spent. I set up a thermometer in the fridge and storage seemed okay.
I guess you guys are blessed with working testis and are sensitive to much smaller changes in HCG quality.
I do not see difference at the day #80.
I had little inadvertent experiment while approaching the end of Novarel vial.
I switched from E3D (T+500iu)
to
E3D (T) and 250iu on days in between.
My balls got somewhat bigger and scrotum hanged lower more often.
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Shortly after I decided that since I do shots every day, and I use same size needle (31ga) for either shot, I may as well change to
E2D T and E2D HCG on alternate days.
Today is my first T shot on this new schedule.