Yeah, I do that a lot too...let it sit in the fridge for months and then remember that I have it. And it always works like new! I just started back on MC's IGF a few weeks ago. I swear I thought that I'd used it all, but I checked my spot in the fridge and I still had 4 bottles! It has to be over a year old, but it is working great. The biggest problem I have is just finding time to apply it every day, because I get so busy and I'm exhausted at the end of the day and just want to go to bed.
Also, I've been using it sub-q the past week just to rip up for the pool season. If you want the great pumps, use it directly in the muscle you are working pre-workout. You will get skin-splitting pumps.