I know people who have left beer in the fermenter for 6 MONTHS on big brews. I personally recommend 3 weeks to a month even for regular recipes. An extra week (or 10) will not hurt anything at all, and will most likely result in BETTER beer, because the yeast will keep working on "cleaning up" after fermentation is finished.
Go out of town, don't worry about the beer, and bottle it when you get back.
"Give a man a beer, and he will waste an hour. Teach a man to brew, and he will waste a lifetime!" Bill Owen