All versions of Java have what is known as an EOL (End of Life) date. This is the point after which Oracle effectively regards it as dead. You can still use that version of Java on your machines (there is no cutoff mechanism) but you will no longer see any new releases or bug fixes. And Oracle’s advice will be to upgrade to a later version.
With the huge delay between Java6 and Java7, we have not had to deal with an EOL for quite a while. But in November 2012, Java6 will reach it’s EOL according to Oracle (full details are here on the Oracle site).
There are often some very good reasons for staying a few releases behind the latest version (especially in critical systems like planes and nuclear power stations) but what about NOT upgrading your version of Java?
The most common issue we find is that users need backwards compatibility with libraries which do not support the later release of Java (it often takes a while for things like Websphere) or there is a new bug introduced. Or the system is setup, it works and there is no real reason (or budget) to update it.
If you have a system which is dead in development terms – ie it works, it will never be altered and you will just run it until dies – you can just ignore the EOL. But if you are maintaining a system, you should really consider some plans to update to Java 7 at the end of 2012. What are your plans?
If you want to find out more, there is a really good blog post on the subject.