ok now seriously, how long has it been sitting at home unused? pretty much all car products do have shelf life.
imo, i wouldnt use turtle wax in the first place. though i cant deny that they havent improved alot over the past few years, trying to get their name out of the "low end wax" category. but anyways, i say if u want to use turtle wax again, go buy a new one! its not that expensive and u wont risk the chance of having bad old wax that might scratch your paint or not protect it well... at worst it might make it look uglier