If a bowl is flavorless, ashy, or burning my mouth, I dump. However, as you develop your technique I'm sure you'll find this will be a lessening problem. A lot of my success has centered around learning to properly tamp. My journey sort of looked like this:
1. Never tamped. Ever. Seems crazy an entire tool exists just for the charring light.
2. Began tamping to manage ashes. Usually extinguished pipe.
3. Learned to tamp lightly.
4. Tamped constantly, obsessively. Every tamp resulted in a relight.
5. Half way down every bowl, pipe went flat or ashy. Began dumping ash half way through bowl, flavor was better, but pipe was hot.
6. Learned to tamp occasionally, lightly, while drawing in on the pipe. This was the game changer. When I notice the pipe is beginning to go out, or taste odd, I tamp very lightly to keep the ember in touch with the tobacco below - I do this while I'm actually puffing on the pipe.
#6 has drastically reduced relights, flavorless pipes, and the need to dump ashes. Its probably one of the most important things I've learned.
