Every two years, in April, Ubuntu releases a fresh long term support distro which will be supported for 5 years. The latest release is 14.04. Derivative distros, such as Xubuntu, also release on the same schedule (though Xubuntu only offers 3 years of support versus 5 for the regular distro.)
I have been running Xubuntu 14.04 on my primary laptop, a loaded T61 motherboard living within a T60 chassis, since about a week before the official release. It is running superb. Everything is working as it was in 12.04, I just have another 3 years before I need to worry about running any major updates again.
So, how do you update your system from 12.04 to 14.04? Well, there are a couple of ways to go about it. I will point you to a blog post which will describe the most "pain free" method of updating your system to the latest long term support version. Be sure you have a good Internet connection and do not need use of your system for a bit. Follow the instructions on the linked post and enjoy your new system. Feel free to contact me if you have any issues or concerns.