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!
where is “update age” ?
You can find “Kill Particles When Lifetime Has Elapsed” in the Particle State module in Particle Update