Belts usually don't wear out, they only get damaged from debris getting caught between belt and pulley. eg rocks, sticks, bits of metal. Most bikes with belts have a lower chain guard to stop this happening,(BMW,Buell, Harley Davidson) and I surprised there is no guard on the S and DS models. DS is designed to go off road where you expect to get a lot of debris.
just inspect your belt and if no cuts or signs of damage, don't worry, would be good to have a spare. But no need to replace unless damaged. Belts are made from Kevlar or better and have improved much in last few years. They used to have a recommended replacement life, but this keeps increasing with better belt technology, also cost is dropping as they become more popular.
Buy A belt tensioner gauge from amazon and make sure tension is correct at 55 lbs or 25kg and pulley aligned and clean.
Gates (krikit) 91107 Belt Tension Tester. Measures tension from 30 to 160 lbs for USA (15 to 75 kg for rest of the world.)