Yes, they can break if you use them for heavy dueling.
If you are careful and don't hit it very hard on things and do not hit it on soft objets such as beds and sofas, it will nor break.
Just be careful and I'm sure your saber will be allright :D
You may want to review Yoda's dueling with you lightsaber tutorlial, it shows you do and don'ts in dueling with you saber.
EDIT: oh my, I wrot hit on soft objets, no no no, do not hit on soft objects!
Where do I keep me head today?