I'm not sure since I don't have my 98 manual, it went with the bike, but I think the recommended interval was 8 years or 80k miles. Maybe someone with the book can verify that. From what I've seen on other forums, most guys go with the mileage, but if your handy than you could probably do it yourself and feel better.
8 years/80,000 seems to be the average consesus as my Two Wheeled friend alluded to. I have heard of some dealers & people even go as far as 100k but I certainly wouldn't. Anyway hope this helps. Ride safe.
I would change the belt with that many years on it. I do not know what Honda recs on that year but as a auto tech for 31 years Ill tell you rubber products break down and gets brittle and hard even when not in use.That includes seals and tires,hoses. DOT recamends replaceing tires that are 6 years old even if they have good tread on them.