Nope, a Mama Hen doesn't need to turn her heat up and down. She also doesn't have night lights under her wings!
While the idea behind MHP is to mimic a broody hen, it can't do that 100% any more than an Eco Glow can. The reason I turn MHP down is for the same reason that folks who use heat lamps raise the height of their lamps weekly.... it's an artificial heat. As such, it can't replicate perfectly what Mom does, and it's a drier heat as well. So I just watch the chicks and when they are kinda of roosting half in and half out at the front of the cave I'll turn the heat down about halfway or raise the frame. Either way, they are content. I start mine at a higher temp than folks who brood indoors do because I start my chicks outside in the run, where I have more dramatic temperature changes during any given 24 hour period.