Keeping your website up to date and modern is worth it every time and you should always place a portion of your budget aside to allow for updating or redesigning your website.
Advertising and listing in Phonebooks and Newspapers are getting to be a thing of the past. Most people will now use Google, usually on a portable device such as a Tablet or Smartphone, to search for a business or services website.
What your clients and customers see when your homepage opens will determine how successful your business is. If you are still trying to hang a business off a poorly executed 10 year old website then you are committing a sin about as bad as turning up to a wedding in a clown costume.