new vial

Hi guys, I've been picking up my standard test cyp prescription in 1ml vials for years. A couple months ago I went to the pharmacy and was told that they don't have 1ml vials anymore so they gave me a 10ml vial. Normally, this would last months but they said it actually expires after 27 days so...

When I get to the very end of a vial of Cyp, I usually just inject whatever is left then get a fresh pin and draw/inject whatever I was short from the new vial. I do this with the idea of keeping the fresh vial "fresh", and not putting the needle from the old vial, which had been punctured...