I use my 26 all the time, with a Slow N Sear. Its pretty foolproof and doesn't need much adjustment most of the time. At 225-250, I need to refuel somewhere in the 6-8 hour timeframe depending on air temps.
If I can find a good deal on a 22 WSM I'll jump on it though, for the increased volume of food it will allow me to prepare. I can easily fit 2 butts on the 26 with plenty of room to spare. 3 would be no trouble, 4 is going to push it with the way the SnS sets up. It might be possible with a snake, but it would definitely be pushing it.
I cooked for a holiday party last week and I was definitely pushing the limits with the food I was making.
For regular family cooks, my 26 is just fine, especially with the SnS. The 22 is great with it, too, but I tend to use the 26 more often just because of the amount of food I'm cooking.