I agree, direct drive vs. belt drive is a non-issue. Belts work fine, most of the time.
That said, I've never kept a belt 25 years. Usually they're looking ratty enough after 10-12 years, that I just replace them to avoid the down time. I keep the old set as backup, so I can avoid downtime due to a failed belt. Still, at 10 years... who cares?
The only legitimate problem I've ever had with belts was when I went thru three OEM mule drive belts in two years on my 60" deck. Damn heavy duty aftermarket PTO clutch was locking up so fast on cold belts, it'd snap them on first engagement (cold). Went to Kevlar belts, which seem to be holding, so far.