I've researched this a bit and recognize it's really difficult to tell for certain without daily testing. I'm just curious whether it degrades slowly as the days pass, or whether it loses its potency rapidly once the expiration date arrives (whenever that may be.) I know bacteriostatic water is supposed to prolong it's longevity as well, I'd just like to know how you guys feel about all this. I ask because I bought some serostim, and each bottle is 18iu. I re-constituted it with bacteriostatic water, but am wondering whether I should use it within a specific time frame. I wanted to start with 1iu/day, but that would mean I'd have the bottle for 18 days and I don't want to waste it by using the product after a certain time when the potency has degraded. Any thoughts here? Thanks in advance!