...
The Age Range refers to the age of the younger and older particle that will be associated to the origin and end of your gradient map (#5) respectively. It is measured in seconds and you must get those age informations from the particle tooltip in RealFlow. General random ranges like 0-1 or 0-100 won't work here, you must find the proper ages in your actual simulation.
Then you can apply that ramp (it must be horizontal like the one shown below) to any attribute on that material (obviously assigned to the uv channel you specified, in this example Channel 0).
If the desired effect is to make your particles to start disappearing after certain age, the ramp may be assigned to map the particles material layer opacity, so the material will start disappearing (and so the particles) regarding that gradient in age.
Mapping particle ages to an UV channel to be later applied to control a material opacity