WordPress is designed to be simple and easy to work with. Most of our clients don’t require any training and have no problems editing the site themselves. Maintenance however is a different beast.
Clicking the upgrade button isn’t hard and 90% of the time, everything will be fine, however it’s still a pretty big risk to take on a live, client facing site as due to the fact that most WordPress websites use 3rd party plugins, unless you’re 100% sure that the new version won’t break anything on the site, you really don’t know what to expect with the upgrade.
You risk functionality issues, downtime and data loss so regardless of who developed your web site, if it’s important to you, you should definitely consider a maintenance contract with a professional development agency such as By the Scruff.
Our approach to upgrading is a little more involved, we upgrade all the plugins we run on live sites on a dev server beforehand to make sure that we are aware of all potential compatibility issues. Then before upgrading we prepare the site and fix all the compatibility issues before they even happen, clone the site with the fixes to our dev area, upgrade the site, make sure that there are no issues and then do the same thing on the live site.