Whereas I never open the cooler to stir until it's time to add the sparge water. I found no benefit to stirring and I lost heat every time I opened the cooler. Of course, with a HERMS/RIMS, heat loss wouldn't be much of an issue.
When I mashed in a cooler I never opened either.
I am still learning this brew setup, and my first 4 brews cam in real low in efficiency.
Since then, I have fixed my mill, and I started mixing the mash and the sparge to see if it helps.
Last brew I pulled 72%, better but with a HERMS I feel like I am still 6-10% low.
Today, I am double batch sparging, it seems that is where I was loosing ground before.