I used the old Adv II I had - also no expiration date. There was a method to my madness. Even if it is less potent - unless it has gone totally useless - it was better than full dosage if it accomplished anything at all. I think it accomplished something, and will likely use another old tube, but maybe a day or so before the month is over - just in case it's potency has been diminished. I think if I am within a day or so ahead of schedule, it should be no big deal. Hopefully, that will take care of the remaining buggers that are escaping the vacuum.I also got Krista Advantage 2 because I know she’s had it before. I have some from before. It has no expiration date. But I only want to do this to her as few times as needed. So might as well get the new stuff.