Laura,
My thinking is you need to do what you must in order to recover at a pace that feels really easy. You dont necessarily need to reduce incline.
I bring down both incline and speed always when Sean says Level 1. I do my Level 1 and Level 2 always at 0% incline. For Level 3 and Level 4, I increase both incline and speed if Sean says to do a Trek. For a hill, I dont increase speed but I increase incline a lot.
Totally unconnected, but for some people they always set the incline of a treadmill to atleast 0.5% to 1% as that is supposed to mimic the extra exertion of running outdoors, so for them a low incline = flat.
~* Vrinda *~