Nope, I keep the MLT covered during the entire mash process.
Yeah I have a copper HERMS coil in my HLT, you can see pictures of it in my build thread.
Mine does not recirculate continuously, only when the mash temp drops the BrewTroller turns the pump on and recirculates until the mash comes up to temp. But I am drawing the wort out of the bottom of the keg and then pumping it through the hex coil and then back onto my plate
I've considered trying a different program and only heating my HLT to the temp that I want to maintain the MLT at and then recirculating continuously. But with a 1650W element it does take a good bit of time to ramp up the temps. So my mashout would add another hour to the process at the current rate, maybe after I upgrade to 220v.
Even though i've made 4 batches so far using my current method and it always comes out awesome and I usually end up in the high 70's for eff.