The search engines are always updating their algorithms, other people are marketing their sites and fighting you for the prime positions. Marketing your site needs to be a regular activity. Additionally, as you add or drop products or services, get a new email address, or change staff, updates need to be taken care of. It makes sense to leave it to the professional while you take care of the part of the business you do well. As important as what is on your site, is where your site is hosted.
Some hosts take on too many customers.
As a result, their servers are very slow. When they're down, you're out of business. Small enough to know you, and take your business seriously. Large enough to get the job done, day in and day out.