We’ve encountered similar problems with having refills take some time to come in. We now try to stay a bit on top of it... but it is hard to remember.

I would probably use an expired presciption that was minimally outdated if we had to. We ’ve always saved the expired ones to be used for training sessions. Since I’ve never had to use it on my daughter, we’ve always had extra for practice sessions with the nurse (we inject it into wadded cotton and gauze). My daughter was taught in the past few years and I’m hoping that one of her close friends would be willing to learn.