(Beginner question) How to make particles expire lineraly in cascade

I made a gif of my current particle system. At the moment it seems the particles expire randomly between my lifetime bounds of 0s and 5s.

If I set both the minimum and maximum lifetime to 5s, the particle system floats away for the 5 seconds, like this.

Any help is appreciated as I don’t really understand why this is happening as a beginner. I wanted to create a solid line with the particles.