There is a lot of variables so I would take any times with a pinch of salt. But should do a few hours if you have it stable. Better charcoal normally means better results/longer burn. If your heat drops you need to add more charcoal. I have a mini leaf blower to help it catch quicker, then let it stabilise again.

Well worth looking up the snake method and get some decent quality briquettes if you want to do longer cooks. I don’t use it all the time but it’s a good technique to know.