Java SE 6 is indeed released in December 2006 and shortly the new version 7 will be released (expected July 28th, 2011). Since the initial release of Java SE 6 a whole bunch of updates are released, a few days ago update 26 was released. So I would not take any risk, just install the latest update and develop/test/run your application with this latest update. I'm quiet sure you won't discover any issue with this new update because these updates are all about bug fixes, performance issues,... Public APIs will not be changed in these updates, more info can be found
here.