As everyone has already answered, LTS's are generally done for systems where you need stability and reliability assurance for long term. Since its a desktop, I believe yes, go ahead with 15.04 update. Take utmost care that you don't go out of power/internet connection etc while upgrading. If you have crucial data in your desktop and you fear that you may get disconnected from the internet or may run out of power and if you don't want the hassle of rebuilding stuff again, DO NOT update.
LTS are generally used for servers.