When rubber timing belts were first introduced, the manufactures recommended replacing the belt at 60k miles. Later, they recommended replacing the belts at 90k to 100k miles.
Toyota and Ford have moved to non-interference engines several years ago.
If the maintenance schedule calls for changing the rubber belt at less then 100k miles, I suggest it is probably an interference engine.
IMHO, your problem boils down to converting miles to hours.
Let's see you drive a mile typically at 45 mph, so it takes 1/45th of an hour which is 1.333 minutes, done at 2000 rpms, thus 1 mile = 2,666 revolutions per mile.
times 100k miles, 266,600,000....revolutions of belt life
divided 1800 rpm, 148,111 minutes, or 2,468 hours or 1,234 hours at 3600 rpm.
Thus, the generator will rust out, or you will move before the belt needs changing.
But we have to factor in dry rotting, so I'd not do it any sooner than 10 years. Maybe 10 or 12. Or inspect it every 5 years.
State your problem, not your diagnosis.