Maintaining Brand Recognition
A well-designed logo can last more than 30 years. The longevity of a logo contributes to brand awareness, so it's important that the design does not reference design trends or a specific time period. It's best to avoid over stylized fonts or design himmicks like gradients and drop shadows that will go in and out of style.
A logo should be legible and iconic. Some of the most effective logos are the most simple - comprised of basic shapes, such as circles and squares. Take a look at Target, Apple, or WWF for example. The design isn't earth shattering nor does it try to convey every aspect of their business. The logos essentially act as a stamp and offer a visual clue to the company name or purpose.
The application of your logo must be extremely consistent. That's why companies (big and small) have brand guides that dictate how a logo should and should not be used. The consistent use of the logo will define its overall success. Most logos are simple and from a design perspective not incredibly interesting. It's the consistent application over and over again that helps the consumer/client to begin to link the brand mark with the company.