If your current Joomla! website was built between about 2008 and early 2011, chances are it was created using Joomla! 1.5x, which was the latest stable version available at the time.
However, software is always being improved and updated, and in recent months Joomla! has announced 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 where possible, to enable longer-term stability for my clients, but sometimes there are compelling reasons to do otherwise and sometimes your site creation may fall 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!1.5x, there are a number of potential issues which I thought were important to highlight:
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 PHP5.3, which is the underlying code that Joomla! runs on, as it is more secure than previous versions (all websites currently hosted by WebSolutionZ are running on a PHP5.3x platform). But "old Joomla" was written for earlier PHP versions, and those older sites won't work 100% effectively on a server running 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 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 actually needs to be a security problem on both the website AND the server. If the server is properly secured, security holes in your website will not allow access. However, if a security hole is discovered on any web server, anywhere in the world, word gets out quickly on hacker websites and there is a good chance that if any of the components installed in your website will allow access, your website will be hacked in the attempt to take control of the server. And if you are running a J!1.5x website, chances are the developer of the rogue component will no longer be developing/maintaining their J!1.5x 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. For instance, many older websites (although none I created!) utilised Flash, which Apple and Android no longer like, so anything Flash won't even be visible on these devices. If your website is more than a couple of years old, there won't be any code within that tells it to display in a smartphone or tablet-friendly way, it will just display what it can of your "normal" website in a very, very small way and ignore the parts it cannot handle.
5. Social media connectivity. Really, you're not doing yourself any favours in 2013 if you don't at least have a Facebook Page for your business, or Twitter, or Google+, or Pinterest, or YouTube, or whatever platform is best suited to driving traffic back to your business website. You may want to add all those fancy buttons and feeds to your existing website, to show how social-media-savvy you are. Problem is, a lot of the time nobody had written nice modules to do that, back when your website was created.
So... you will probably want/need to upgrade eventually. But...
1. Unfortunately there is no simple upgrade path from J!1.5x. This is due to a number of factors:
So rather than being a simple upgrade, moving your site from J!1.5x is actually a full migration, which involves creating a new site and migrating content. There are some tools available which allow us to migrate existing content that is within the core components, but these tools don't always recognise all content for all third-party components (as there are thousands!) and it doesn't migrate the site template. So migrating a site is something that needs to be considered and planned on a site-by-site basis.
On some sites we could just create a new site/template and migrate the content. On others it may be simpler to create the new site/template and copy-paste the content, depending on what third-party component it is currently sitting in and how much content there actually is.
2. Many of the images used in 2008-version websites were much smaller and lower-resolution than those used on today's websites because bandwidth and screens were smaller back then, so often it is better to source new, higher-res images rather than re-using 2008 ones. And as previously noted, in some instances components were used that are no longer available in J!2.5x, so we would need to source a new component and recreate the content.
3. If you have had specialist Search Engine Optimisation (SEO) work done on your J!1.5x site, depending on how it was done, this may not be migrated and may need to be re-done.
4. Timing. As noted above, J!3.5x LTS is due for release in March 2014. You may decide to wait and jump straight to that. However, this may be more complex if there are no 1.5x -> 3.5x migrators available.
The Joomla! developers have indicated that future versions would be either mini-migrations or one-click upgrades. Ultimately the decision as to whether you want to keep your existing site going until something breaks (and perhaps by then J!3.5x will be the current LTS), or whether you prefer to migrate now, is entirely up to you. As a rule of thumb, I would suggest:
If you are interested in discussing this further, please don't hesitate to contact us. :)