Only one Panasonic Lumix camera I know of has a recording time limit, the LX7. Of course this omits EU models that are limited for tax purposes.
I also am not aware of any overheating or other issues that limit shot length on any Lumix cam. These issues appear to be a specialty of Canon and Sony by my research. Even the tiny little GM1 will drain the battery before stopping, although they limit the max frame rate in that camera to 30p/60i instead of the 60p available in the G6, GX7, and GH3.
Yes, I'm a Lumix G series fanboi.
Fran