It may be time for you to Burn It! A general guideline is to Burn It when your Traveler’s Checks will double. Although burning down the building resets your funds, Virus Installations, and Interns; it also grants you a big bonus to all your Floors when you start up again. This means you’ll level up faster, and hopefully be producing enough money from your Floors to reach a higher level than before you retired.
For more gameplay tips, check out the Kongregate forums!