I would never use "life" to control when particles are present and when they're not. I'd use "number".
But this may be the long-standing "green particles" bug. For some life values (very long usually, but maybe for short ones too) the particles turn green at some point in their life, even though there is no green in their color gradient. It's something to do with the number of gradient points, and the amount of time the particle is alive. I'd suggest messing around with the color and/or transparency gradient, and add/remove points.
Or perhaps use "size" instead of "life". (Although I would personally still use "number" -- creating 100 particles that have a 0 life or 0 size still takes some time and memory.)
I would not have thought to use Number as Life seemed more appropriate but now I'm wondering why I thought that!
The green bit is misleading as my particles are green! I've just reloaded the program and the green blob is now no longer there until the emitter has fired once - then it remains for the whole animation. Reducing the Life percentage to zero gets rid of it (and everything else) Increasing life makes it longer. No matter I will either sort it or use your number method!