Try something like this:
Emitter Update:
SpawnRate - 1, MaxLoopCount - 1
Particle Update:
(Update Age) Kill Particles When Lifetime Has Elapsed - unchek (False)
In Niagara System, on Timeline set length of Emitter to 1 sec.
I hope it will work, maybe with some tweaks.
Does someone know how to create immortal fx in niagara? In Cascade It was super easy- spawn rate 0, burst single sprite, lifetime 0, and basically you have immortal sprite. But how to do this in niagara?!
This works… but not in version of editor I must use because there is no “Kill Particles When Lifetime Has Elapsed” checkbox 
But Thanks!
You can find “Kill Particles When Lifetime Has Elapsed” in the Particle State module in Particle Update