It's best to get the backing of your editors, so it's not your responsibility to keep it up to date. Consider keeping information on the company's top executives and board members, pay, home phone numbers and annual meetings. The goal is to press a button once a year and have a ready-made story on executive pay, minorities on local board of directors or interlocking directorships. All the while, you'll have a useful database that can be used to make sure you don't miss annual meetings, documents or other scheduled events. And it'll store home phone numbers you need in a pinch.
Revisions are a nightmare.
You'll hate what your job has become. Instead, make friends with the economists in your state university system who do this for a living. Build when you have to, but consider how often it will require maintenance and who will do it. For corporate records, it's a half-hour a year for each company you cover. For economics, it's a half-hour or more a month for each indicator you track.