Nature Spirit DI

After reading the Vengeance/Devine Intervention discussion, I got to thinking.
Does a Nature Spirit expire or is it killed?
Would DI cause it to be permanent?

Both, the Nature Spirits have a set time that they will stay there, but they can also be killed by the enemy. So DI would help it if it was being attacked, but other than that I don't believe it would be of any use to your Spirit.

Well Vengeance has a set time too and it gets made permanent.
Sure would be interesting to test and see if the same loophole exists.

Could an alpha test this, please? I'd like to know if this would work, as well.