Keeping your website up-to-date by contracting with a web design company or programmer can be quite expensive. Companies can charge anything from £50 per change to a daily fee.
If you know this is going to an issue it would be worth getting some kind of contract set up with your web designer. A small regular monthly fee maybe the best way to go as you then do not feel pressurised into leaving changes as long as possible. Some months you may make no changes and others you may make several. Setting out what defines a change and what is seen as more than that should perhaps be clarified within the contract to protect both programmer and website owner.
Duo like many web design companies would be happy to set-up a website support contract were we are happy to spend up to a set amount of time per month on keeping your site up-to-date. We would of course base the charge on how much you expected to change per month and perhaps set a time limit - ie 2 hours worth of work per month.