I agree that once a month would be fine. I CAN see (and often have done so myself, in the past) easily consuming 6K cals in a day. One day at camp last month I had 4K in one day (a lot of it beer) and I was really restraining myself.
I would, though, make sure to limit that to once a month, if you're trying to lose weight.
47 M 5'8"
May 4, 2010...... 440? lbs. (Start FitDay Size 60 Jeans)
June 19, 2010.... 393 lbs. (First Weigh-in)
June 19, 2011.... 229 lbs. (164 lbs. gone in one year :-)
Current Weight... 185 lbs. (Size 36 Jeans)
Next Goal 169 lbs. (07/04/12)
Ultimate Goal 165 lbs. (12/31/12)
The best exercises for weight loss are Fork Putdowns and Table Pushaways.