My wife has a 10 year old car that is used soley to get to and from work. It runs well, it still looks nice, and it gets great gas mileage. The only negative factor is that is burns through a quart of oil each month. Let a few months go by and I begin hearing the knocking sound of unlubed lifters in the engine. At that point, it desperately needs oil.

Luckily, the engine did not lock up. Isn't it nice, though, that our cars tell us when they need oil by flashing the oil light? Unfortunately, your website doesn't have a warning light like this to tell you when it needs some maintenance.
Like a car, you must keep you website well oiled so it runs smoothly. And by "running smoothly" I mean your website is engaging visitors so they either buy or move to the next step in the buying process.
Keeping your website oiled takes continuous effort. You must make relevant updates frequently. You must provide quality content to engage your visitors and keep them coming back. And you must constantly measure the results.
To do this in a cost effective manner you need a proven web content management system. A good web content management system will provide tools to update your website without the need to call in a programmer. A good web content management system will also provide you measurement tools to help you guage your website's effect on your bottom line.