I’ve never owned a pair of the mx3 so I can’t compare but I have the mx4 and they don’t match your description: the battery life _without using the case_ is fantastic (8 hours, plus 24 hours using the case) and the connection is very consistent and reliable.

I don’t know how good they’d be for your use-case, but definitely worth considering the mx4 as distinct from the mx3.

edit: xm4 not mx4. Shows how little I care about headphones :-D