In my experience as a young competitor, coach, adjudicator and back to an (older!) competitor, I've watched and experienced what it takes to keep up on the competition floor. It breaks my heart to see great dancers falter and fatigue early, which often costs them a place or two. I also know how it feels when your lungs are burning and your muscles are weakening!
Now that I've experienced life a little more (having two children and a body that tells me "no" more than "yes"), I realise dance training on its own, doesn't give me the results I need. My personal favourite is Pilates, which comes from dance. It trains me to breath properly, which is a vital thing, many dancers struggle with! Holding your breath in order to execute a group, can only result in fatigue!
Suna Pilates ( www.sunapilates.co.nz ) enables me to maintain my flexibility and focus on specific weak areas of my body. Good body balance can not only help avoid injuries, it can reduce fatigue and keep me dancing much longer! Their classes are always fun and the instructors are very good at keeping our technique in check for there best results!
You can also try other dance styles, weight training or something else that ISN'T your regular choreography or dance style. Whatever you choose, you need to ensure it compliments your dancing and is FUN!!!