My '92 Si HB has sat idle a lot, has only 72,500 miles in 16 years. Timing belt change interval is 90,000 miles or 6 years. Is the 6 years valid, or just another way for Honda dealer to rake it in? I don't drive it hard, 4,000 rpm max. Do these belts rot away with age? Safe to wait until 90,000 miles?