Tobacco Ash: Heating, Cooling, or ???

[4dotsasieni]

What's your opinion on leaving ash in the bowl on top of the burning tobacco? Does it heat up the smoke, or cool it down, or neither, or something else entirely?
I tend to lightly tamp down the tobacco a couple of times a bowlful, and just just invert the pipe and let the loose ash fall out. I figure it just heats up the tobacco beneath it, but someone has suggested that it actually keeps it cooler.
What are your thoughts?

 

[briarfriar]

I find it serves as insulation to slightly cool the bowl in your hand, but it is necessary to empty the ash once in a while so it doesn't smother the burning tobacco.

 

[papipeguy]

My guess is that it depends where the hole is drilled. I don't understand what advantage there is to ash near the air hole. I just dump the whole bowl when I'm done and start fresh.