Previously, we've covered why it's essential to keep your WordPress website, plugins and themes up to date and the same rules apply to sites running any content management system (Drupal, Zencart, Joomla!, etc) but what if you don't? What, aside from the security implications, are there for your website?
First of all, you're going to have to update your website software at some point, let me explain. You can’t keep running an old version of your site software forever. Some day you’re going to want to use a new theme, and your new theme is going to require the latest version. Or you’re going to install a new plugin or module, and it will require an update before you can even start the process.
The more frequently you update your site, the less likely it is that updates will cause you problems. Issues will arise if you try to skip a bunch of version numbers (for instance, if you try to update from version 3.6 to version 4.5 of WordPress).
Another important consideration is downtime, if you update frequently your site will be down for a few minutes at a time. If you don't update for a while then you're going to have to take your site down for longer, maybe hours, to apply all of the updates in the correct order and test that everything is still working.
We've encountered this scenario time and time again. Whenever someone gets in touch and needs some changes made to their site, we'll first take a look at what their site is running and what version they have installed. Usually we'll see that their site software is really out of date, and, most of the time we don’t even try to update it. We normally advise clients to start afresh with a new site, and import their old content. For a small site, this might not be a large task, but for complex sites, it can get very expensive.
In a worst case scenario, this can even result in data loss. We once worked with a website that was running a very old version of PostNuke (a very early content management system that was created back in 2001 and hasn't been supported since 2008) with a phpBB forum bolted on. They hadn’t updated in years, there weren't even any new versions of PostNuke available and they wanted to update the forum to add some new features. We spent two weeks working on a method of moving their 90,000+ forum posts and 3,000+ users to the latest stable and secure version of phpBB and the rest of their website content to a new WordPress site – totally abandoning the already abandoned PostNuke software.
You might think you don’t need to update because everything is working just fine right now. But in the long run, not updating will cause far more problems. Updating is relatively risk-free, and is a very important part of owning a website.