every 5000 km ay inspection lang yan, just check lang kung may cracks, and you can even spray it with belt dressing. pag may cracks na saka lang palitan.
normal replacement interval would be around 30,000 km or more. nasa manual mo yan pards check mo lang.
20000 km for fan belt replacement is too short an interval.
yep minsan mas ok preventive maintenance, safer pa especially with cars w/ 1 belt that drives the waterpump, alternator and powersteering all at the same time.