The smallest sprocket has already been replaced once. So its relatively new. The one next to it (7/8) is original but still looks pretty good. I usually push my bikes hard so parts wear out fairly quickly. Given that my favorite gear sprocket is almost new and the 44t chain ring looks to be in good shape I may just get away with replacing the chain only. But, for now I think that the best option is just to ride it as until it starts to show signs of slipping under load. Thanks for the wisdom.. the guy at the LBS was sure that chains must be replaced at 3000km.