People say that when you modify one unit, it modifies them all! This trick teaches you how to get round that and to give one unit in a group of identical others a lifespan! i.e. it dies after a certain time.
#Now make it convert back to the orginal player. Converting it to nature then back will not work, do the above method because I know it works!
#First add a change units in area trigger, select that anubite and set the radius to 1 or 2 so it will only affect that unit - make it change player to a nature anubite keeping the same unit.
The anubite will keep it's lifespan when it converts back and will die after the set lifespan time in the modify protounit trigger!