At most you should change it every 100 000 km...which is..humm 60 000 miles i think ? When i bought my 94 lx escort, the car had 65 000 miles on it and the original belt..i changed it just in case and i inspected the belt...looked fine to me but you don't want to mess with this kind of stuff,cauz the repercutions are too important
The first time mine got changed since the car was new was in the neighbourhood of 180 000 - 190 000km (off top of head). The old belt was still in not bad shape, but boy did a new belt make a difference. Could literally feel the performance increase 8O
It was one of the first things I did when my Dad gave me the car.
Well i know the belt's life can be easily extend.. especialy if you don't beat the sh*t out of your car and if you grease all the components of the serpentine system....but it is strongly recommended to change it after 100 000km...might cost you some money...but it will never cost more then if your belt break while you are far away from home and you end up having to get your car towed
I also have a '97 lx and I went through the same problem of trying to figure out when to change it. It seems like Ford didnt put a spec on it for the first year of the 2.0 SPI engine. I have seen some places say go to 60,000 miles, others say 100,000 miles.
I bought my car with 101k on it, and decided I should change the belt. I was a few hours into it just to get to the thing, then I saw that the belt looked almost brand new. The previous owner must have had it done at 100k (he kicked the bucket, so I couldnt ask him)
I would get it done at 60k just to be sure, rather than take the chance. ITs a pain, but worth it.