Since I smoke mostly while clenching, hardly ever removing my pipe, most of the time I know that I have finished when I get a little ash in my mouth. Even on my pipes that have a few mm of chamber below the draft hole, which perplexes me when guys complain about pipes drilled like this.
My pipes all cake down into the heal and into the shank, so I usually don't worry about this. But, on the rare occasion that I taste warmed briar, I always just stop and let the pipe go out. You can always tell when the briar is getting super heated, if you can distinguish the taste of warmed briar. If you can smoke to thew bottom without smelling warmed or burnt briar, then there's nothing to worry about. Your not going to burn the briar without tasting it... unless one has shit for tastebuds. YMMV
And, to cake in the heal... I am more baffled by guys who say that they never get cake in the heal, as I have to use a small drillbit in a hand vise to clear the passage to the draft hole occasionally, because it cakes over.
But, to guys who leave dottle... no problem with that. They would have a word for that if it wasn't a thing.