coal build-up

It's been around 0 degrees the last couple of nights, and I find that I want to add wood more often, to keep it toasty when we're home. But there's a build-up of about 4-5" of coals on the base of my insert. Is it o.k. to keep adding more wood, or should those coals get burned down to ash before a re-load?

When it gets that deep I let them burn down a bit. I'll do it during the afternoon, when the sun is heating the house and I don't need the stove as much. Otherwise it makes it hard to fit new splits in, with all that coal in there. After its down to an inch or so, I'll load it up again.

-- Mike