Hi Ron
That night we were in the high twenties with snow.  It was last winter, so I don't remember my vent settings.  My cooker is easy to regulate to 250 degrees at the lid.  It usually loses 10 to 15 degrees during the night (7 to 8 hours).  I have never gotten up in the middle of the night to check it since my first cook!  When I get up in the morning it is usually perking along at between 225 and 230 at the lid.  I give each of the legs a tap with a 2x4 and open one of the bottom vents about 1/4 more, and she usually starts back up to 240 for 3 to 5 hours without additional fuel.  That's why I was amazed when I woke up on that snowy morning to find her at 170 with only a few briquettes left.  I remember that I did have my vents open farther than normal when I got her regulated the previous evening.  I didn't connect the higher oxygen requirement to a higher fuel burn until after I had got her running again and then sat down to think about it.  Makes perfect sense now.  I've had a few cold cooks sense.  Now I just pile in more fuel.  The rest works as normal.
I'm kind of fundamental about water.  I always use it.  I file that one under "It ain't broke, I ain't fixin' it"!  I use the larger Brinkman pan (I've lost the little one that came with the cooker).  The great thing about a long cook with butts or brisket is that the pan will fill 1/4 to 1/3 with rendered fat, and still do it's job using the fat as the heat sink!
Cheers
Lou