Yeah, I would think you have other issues to look at besides your fuel if you are only getting 6 hours off a full basket of charcoal. I had my 22.5 run for around 24 hours on a full basket before. Even in bad weather, I can't see that dropping to a quarter.
Did it actually need more fuel, or did it ash over and just need a couple of love taps to the legs to knock the ash off?
I built a fire basket for mine (see link in my signature). I would fill it to the top with charcoal and use the flame thrower to light 6 - 8 coals on either the middle (unassisted) or the vent side (when using the Pitmaster IQ 120). It would slowly burn through the rest of the coals as needed. I also had the gaskets and the SS door, so my WSM was very well sealed.