Well, its my second attempt to use the supplied color filter with my Nikon SB-900 today, as I tried to capture the boys in action while they play in the bedroom. According to the manual, these thin color filters will wear down with use and are to be replaced when the heat of the flash breaks the color compound of these filters.
As for the state of it, I have been assured by Nikon that they will still work even when crumpled. The Nikon SB-900 Speedlight comes supplied with four color filters but the truth I now learnt is that it can effectively be used to nullify/introduce a specific light spectrum to your scene when needed.
For example, in a incandescent scene, the use of the greenish filter G1 will effectively bring the whole scene back to a whitish fluorescent ambiance. However, using the G1 or A1 color sets on a fluorescent scene will immediate introduce a greenish or orangy hue into your picture respectively.