I don't have to have the vibrations vaginally so if a vibe I'm penetrating myself with dies I continue as is. On the other hand, if a vibe on my clit dies I must replace it with something other. Fingering after vibration doesn't do it for me. If I have nothing to replace the vibe (no batteries in remotes etc.) I wait a bit and then go at it with my fingers.

I usually grab a different toy to finish up with. It really has never felt like a mood breaker to me.

It's usually not a mood breaker for us either. I'll grab a different toy or switch batteries, whichever feels most natural at the moment. But I always keep spare batteries in the toy chest, so they are right there and totally handy. I like to be prepared and have everything within arm's reach for convenience's sake. That way you don't have to get up and rummage through the junk drawer looking for new batteries.

To be totally honest, I'm actually so anal retentive, I now almost always check the batteries before we start. I'll only keep the same batteries in a toy for about 2 sessions before switching them, because I like battery toys at full power. Doing that, we haven't had a battery die mid-session for quite a while. We have had toys break mid-session, but that didn't have anything to do with batteries. Oh the perils of a good sex life! LOL

I grab another toy. It's quicker than changing the batteries. Most of the toys I use are actually rechargeable though, which basically forces me to grab another toy while that one charges.

I will either grab another toy or switch the batteries if I have some handy.