michiganjfrog, I have opened my M6 with a small plastic tool that came with a replacement iPod battery I purchased for one of my other players and it was quite an easy task but not something you would want to do oftern as i would imagine the small locking tabs would become worn and the cover loose. The battery is not a standard replacement size or shape as I think they have them made at specific dimensions for the player.
My understanding is that new batteries can be ordered from Meizu and a 3 + year life span is touted by them which I think is quite a realistic expectation. I also think that Meizu will be around for many years to come.