- particle system 1 - mark where all particles are fully created
- duplicate that system
- move the beginning of particle generation for system 1 forward in time so that the point where all particles are fully created is at the last frame of the animation
- for second particle system, at the point in time where system 1 starts, put a keyframe on birth rate
- then on second particle system, move one frame AFTER system 1 begins and keyframe the birthrate to zero - this makes the particles die off here