they can be used anytime with good/great effect
you just use them as a supplement to your lights that are there already
where lights are static they create shadows under the leaves so the light doesn't penetrate much beyond 24" below the canopy (600w)
even by moving the light(s) continuously back and forth a small amount it will help the light get further down by changing the angle of light penetration
if you want to see how they work, just move one of your current lights back and forth a foot or so, and see how different parts of the plant below the canopy get exposed to the light that were previously in shadow
they have quite a big effect on the lower buds formation
they're not cheap, its an investment like all equipment
the one i had still works now and i've had it years. It is only that my current room design doesn't fit it, as i have ballasts above the lights, that i'm not using it
you can get extensions for the track also, so one motor can move multiple lights. With the extension you get the extra track and a little trolley that freerolls along the track that the next light hangs off
if there was a downside to them, its that you have moving cables which can be a bit unnerving the thought of them getting caught up somehow.
also, the track can be awkward to put up. we mounted ours to a piece of 6"x1" and secured that either end of the enclosure
all in all though, top piece of kit