well, if you can no longer start the car with one click and hear the slow crank.
i just replaced my battery recently kasi nadischarge siya (left the fog light on) then when re-charged, hindi na nakabalik sa dati so pinapalitan ko na. Then nalaman ko na 2003 pa pala iyon (from the number code) so 5 years ko nagamit yung Motolite Enduro 2SM & I replaced it with the same brand. After 3-4 years I think ang palit unless you see the signs of hard starting. Better still, have your electricals (alternator, regulator, starter & wirings) checked prior to replacement.