You can disperse the wood chunks throughout the charcoal before lighting so chunks will burn as the fire spreads. I actually prefer lighting wood chunks with my charcoal when I start. That way, I get a solid smoke ring right from the start.
Here are a couple of tricks I use for longer burns. First, I use my wet dry vac to clean out ashes after any long burn. That way, I have a consistent cook and cooker - no unburnt pieces from the previous cook to catch fire, no airways are blocked, no mid-cook issues with too much ash. Second, there's no need to go up to 750 to burn off drippings. I had my XL BGE up to 450 two weekends ago to burn off mold and other stuff from not using it during the winter. About 2 hours at 450 did the trick. Third, like Dave recommended, use larger chunks of charcoal for long cooks. The cooking temp will be lower than using smaller chunks of charcoal (there's less surface area to catch fire, especially when lighting the BGE like Dave recommended in a number of areas, and at a low temp, the larger pieces will take that much longer to light up completely). Fourth, gradually get up to temp; don't go too high and bring it down. You'll use more fuel the higher you want to go - if you start low, and keep the fire going slowly along, you won't use much fuel. There's really no reason why you can't do an all night cook with a full firebox if you start with a low temp, around 200, and keep it there.
Lastly, if you have any concern about not having enough fuel to get through a cook, take whatever you're cooking out of the fridge early. It's amazing how long the center of a pork butt will stay cold after you pull it out of the fridge.