How to switch off device experiencing a bootloop?

I messed up a TWRP flash and the phone is stuck in a boot loop, I know why the flash failed and that reflashing it to stock should fix it. Though there's a problem. The home button does not work. So far, I've gotten around that by booting to recovery and bootloader using adb, but that doesn't work with it sitting on the "Samsung GALAXY A5" title screen. I know that the home button needs to be fixed to get anywhere with this, but what's worrying me is that there isn't a way to switch the phone off. Holding down power or power + volume down does nothing but send it into another cycle of trying to boot.

Should I just let the battery run out? Looks like it'll keep going for some time since it was on full charge when I did the flash. It will be some time before I can get the home button fixed and don't really want the phone vibrating every 2 minutes for what will probably be days.