Well I spoke to Animas on this. They said the expectation is that from Low Battery warning to Replace Battery warning is 30 minutes and from Replace Battery to system shutdown is an expectation of 3 minutes. They were not aware that these timings/windows are hugely increased with alkaline batteries. They advised keeping spare batteries by the side of the bed, which I already do. They accepted that the narrow window of warning on the lithium batteries means there is a significant likelihood of the warning and failure all occurring during sleep. They accepted that doing a full cycle of battery change, detach canula, rewind, load, prime, reattach canula is not ideal while asleep in the middle of the night. They are asking R & D to see if it is possible to set a more sensitive battery alarm threshold when a lithium battery is in use, and vice versa for an alkaline battery. They supported the approach of using alkaline batteries to avoid this problem. When asked, they had no other suggestions. They did not make the suggestion of changing batteries early (ie at 2 bars), as was suggested here.
@Engineer88 I don't know why you think I am "making this too difficult"? I'm not "doing" anything. I'm reporting a problem I had with my pump - on the forum, and to Animas. I don't have a problem "changing the **** batteries", but I'd rather not have to do so in the middle of the night, and I particularly don't want the risk of sleeping through a pump shutdown. Of course there are workarounds. There are always workarounds. But I would rather have a pump that engineered around this problem so that users didn't have to come up with undocumented workarounds.
As #donnellysdogs said, this is how the devices get improved, when we give feedback. And Animas has taken it on board, which is good.