I know the wisdom is that you should change chains and sprockets at the same time as a worn out chain will wear out new sprockets quickly and vice-versa. I'm thinking of putting a 16T front sprocket onto my bike which has 5000 miles on the original chain / sprocket and which has been Scottoilered since new, so is it prudent, or just a waste of money, to fit a new chain / rear sprocket at the same time?
If you change the fronts when they start to show wear you'll usually get more chain life anyway. They wear 3x faster than the rear. With an oiler the chain stretching to match the sprockets if the main life eater.