I bought a 1991 ST1100 with just over 17400 miles on it back in July. The original owner rode the bike for five years then parked it in his garage...with only occasional starts/short rides until I bought it. Rode it for around 300 miles looking to shake out obvious bugs...found none. Given my experience with a similar taled 1978 GL1000, I couldn't convince myself to just trust in the force. Took it down the first week of this month to replace the belt. The 'old' belt is original, no cracking, scrapes, or other signs of deterioration. I turned it 'inside out' looking to open any delaminations and found none. The flexibility of this belt feels the same as the new replacement.
Not being a crystal ball type, I feel better trusting the bike after the change...but...I see no reason this belt could not have made it to 100,000 miles or so. Just no age related issues I am familiar with Honda's earlier attempts at timing belts.
Think they finally got it right.