Most of my crafts are put together with either Low-Temp Hot Glue or Elmer's Multi-Purpose White Glue.  If something ever comes loose all you have to do is dip the end in some glue and put it back into place.  If you are really not comfortable making a repair, PLEASE call me or email me, I'll be happy to help you in any way.  You can gently fluff the floral sections of the centerpieces either when you first get them or when you take them out for the holidays.  When you put them away, always try to store them in a cool place and cover them with a light sheet of plastic, that way dust doesn't build up on them.  They will look wonderful for many years.  ENJOY !!!