Nuke stuff - basic shortcuts/hotkeys

shift-x to swap a/b 1/2 inputs.
ctrl-shift-x to detach from network
ctrl-shift drag onto, to replace node

killing nparticles with fields

Anything that works on old Maya particles should work just fine on nParticles.

I can't access Maya here right now but it should work just making a new event and deselecting emit and split and selecting kill original particle.

A more fun way is to create a volume axis field and check to see whether the particles are being affected by it.

If you set your particles lifespan to lifespanPP, you will need to set the lifespan in the creation expression, you can then set the particles lifespanPP to -1 when it enters the field. When you are in the expression editor you will see under attributes ones called inputForce
these correspond to the various fields affecting your particles. I believe they are numbered from 0 based on the order of which they were added to the particles.

So your expressions would look like.

Creation

lifespanPP = 3 + rand( 1 , 2 );

Before Dynamics

if (inputForce[0] > 0)
{
lifespanPP = -1;
}