For the sake of clarity
+NiMh's actually have enough amps for vaping, their power density puts them roughly next to LiMN
+NiMh's last a lot longer (in terms of charge cycles)
+NiMh cell types are a lot easier to replace since they are sold literally everywhere
-NiMh's do suffer from memory effect but modern ones aren't all that bad and can shake it pretty easily
-NiMh's have about half the energy density of high end Li-ions
-NiMh's are generally produced in cell sizes/voltages that are not suitable for direct application on the heating element with a single unit
In my book though, all sources of electricity are suited for vaping

they just need the right kind of pampering. Not very long ago when I lost the batteries i had packed with me and the rest was back home, I resorted to lugging around a small 6v led acid which got me through those weeks like a champ!