If your current Joomla! website was built between about 2011 and 2013, it was probably created using Joomla! 2.5x which was the latest stable version available at the time.
However, software is always being improved and updated, and Joomla! operates according to an official release cycle which includes Long Term Support (LTS) releases that are officially supported for about 4 years, and Short Term Support (STS) releases which are only supported for a matter of months.
I've always tried to build websites using LTS releases, to enable longer-term stability for my clients, but sometimes there are compelling reasons to do otherwise, and sometimes your website creation may occur towards the end of a current LTS so you would not necessarily get a full 4 years. Four years!! It's worse than buying a car! :)
While many websites are still happily running J!2.5x, there are a number of potential issues which may occur (mostly out of your control), which can impact your website:
1. Web servers. Problems may arise over time as underlying hardware, operating systems and software are upgraded to newer versions. For instance, most decent webhosts nowadays run at least PHP5.5, which is the underlying code that Joomla! runs on, as it is more secure than previous versions. But "old" Joomla was written for earlier PHP versions, and sometimes that old code won't work 100% effectively on newer PHP. Sometimes it's possible to perform minor hacks to force a site to keep functioning, but it isn't a happy relationship. So when a webhost installs a new, faster, bigger hosting server and moves all of the hosting accounts across to this new server, sometimes older websites will break and sometimes, they can't be easily fixed.
2. Browsers. Every web browser renders (displays) websites slightly differently, and newer browser versions are designed to read websites coded in a particular way. Older websites couldn't be tested in browsers that hadn't been invented yet, so sometimes a new browser version will render your older website incorrectly. It may be difficult to find a fix when your older website's code is no longer supported.
3. Security. Websites and web servers are constantly being probed for potential security exploits. The goal is generally not to hack your website, but to gain access to the server. In order to hack a website, there needs to be 2 conditions in place - a security problem on the website AND a security problem on the server. If the server is properly secured, security holes in your website should not allow access. However, once a security issue is discovered on any web server, anywhere in the world, there's a good chance that if your website has that issue, your website will be attacked in an attempt to take control of the server. This may not break the website, but it could have other effects such as increased bandwidth or disk usage. The problem is, if you are running a J!2.5x website, the developer of a rogue component may no longer be developing/maintaining their J!2.5x version of the software. Additionally, many webhosts do not look kindly upon old software that is full of security holes on their servers.
4. Smartphones and tablets. Websites don't magically just work on a smartphone or a tablet and in 2015, responsive web design is highly recommended. If your website is more than a couple of years old, it probably won't contain code that tells it to display in a smartphone- or tablet-friendly way, so it will just display what it can of your "normal" website in a very, very small way and ignore the parts it cannot handle. This may impact your SEO results.
So... you will probably want/need to migrate to the current secure version eventually. The good news is, it is much, much simpler to migrate from J!2.5x to J!3x, than it was upgrading from J!1.5x!
A migration includes some/all of the following steps:
The migration can be performed on an offline development server and uploaded once it is finalised, to minimise downtime. You will also receive a new, customised User Manual.
The cost of migration depends on time - the number and type of third-party extensions currently installed, and whether the current website template is to be maintained or replaced. The quickest and cheapest migration is one where the site ends up looking exactly the same on the front-end! But if you're missing things like social media, now is the best time to add it in.
I'm encouraging all Joomla! 2.5x version website owners to migrate to Joomla! 3x, as J!2.5x is no longer supported. It's usually a good idea to plan a migration before problems start occurring. If there are no issues currently, there may be less immediate urgency - but you shouldn't forget about it!
If you are interested in discussing this further or would like a quote, please don't hesitate to contact us. :)