You maintain the temps for the length of the fermentation. Letting the finished beer warm up to room temperature for a week won't harm the beer. Your risk for diacetyl and other fusel alcohols comes mostly in the initial few days of fermentation. Warming the beer up after the main fermentation is complete for your diacetyl rest is just fine, and helps to rouse the yeast.
Beer so good, it's frightening.
2014: Seven Heavens Series One: Vilon, Mystic Melomel, Skeeter Pee.