PFlow Particles not emitting smoke over time

[Jordan]

cool that's all I was originally asking for, but how do you change the lifespan parameter?

Kill the particles earlier?
The graph is a percentage of the life span, so if your particle spawns at frame 10 and dies at frame 20, 0 on the graph would be frame 10 for that particle, 0.5 would be frame 15 and 1.0 would be frame 20.