Timing Belt-18 years old and was perfect

[garygbnj]

FYI-I know that the timing belt should be replaced every 4-years depending on who you talk to. The belt on my 95 TT was done 18 yrs ago (24k miles of use) by the previous owner. Due to the age I opted to replace it with the 120k kit per the advice from various forums. Upon removal of the cover it was found that the belt was perfect. Some signs of reasonable wear but it did not need replacement. The car spent its life in GA & FL. Is there some more specific parameter to know when to apply the age measurement to cause replacement? My mechanic is going to create a covered "window" to visually be able to check the condition of the belt rather than arbitrarily changing it at 4 yrs or 8 yrs. The car will be a "Sunday" driver.

[nissanfreak12]

Even though it looks perfect, seems perfect, 18 years will do a lot to rubber. More than likely it is dry, doesn't have the elasticity it should(even though timing belts shouldn't stretch, still needs to a little bit.) It is the same principals as tires,anything over 10 years old should not be used, rubber loses its properties after a certain amount of time, unless stored in a climate controlled facility.