We take care of website updates for clients on a regular basis, making changes once or twice a day for some and once a year for others. We provide this service under contract for a fixed price or charge by the hour, whichever is most economical for the client. Either way, we make changes the same day we get an email from the client... sometimes within the hour.
Take a look at the sites on this page which we update. The one thing they have in common is that we created the sites and we made them easy to update. Can we update sites we didn't create? Sure we can... as long as they aren't .asp sites or sites created using php or Flash. We work in html and code search engine friendly sites that get found and indexed quickly by Google.