You have a layer of CO2 protecting the beer, so if you don't go crazy, it'll be fine. Keep the yeast at least as warm at the end of fermentation as it started, and you'll typically be fine. I use a keg bucket and an aquarium heater, works awesome, < $40.
Give a man a beer, waste an hour. Teach a man to brew, and waste a lifetime! Bill Owen quote
Why does Happy Hour limit happiness to 1/24 of the day?