Lifeless and Does Not Heal are different. Lifeless is immunity to some spells, and e.g. Liches and Masters Liches have it, and Lifeless beings heal hp the normal way. Does Not Heal + Magic Being == heals in a lab.
Lifeless make you immune to regeneration from spells, items. Possibly innate regen as well. If innate regen works, you can keep Lifeless, if not, get rid of it.