My 98' 100 series has only 49,549 miles on it and they say to replace the timing belt at around 90,000 miles.Since the truck is almost 9 years old come this april, should i have the timing belts checked out or wait till 90,000 miles which could be another 7 to 8 years or so.Will the belt last that long or is it prudent to just go ahead and have it changed....