A practice that I have followed for nearly 30 years, is to have two chains for every drive sprocket. That way when one chain is off being sharpened, the other can be used. When the two chains are finished (can't sharpen them any more), then I buy two new chains and a new sprocket (Stihl brand name). The reason given to me, was that the sprocket will wear down at the same rate as the chain drive links. If you put a new chain on an old worn sprocket (or a new sprocket on with an old chain), the sprocket apparently will wear down very quickly to try to match the chain. I bought into this argument when I first bought my Stihl saw and have followed the practice with dozens of chains over the years. I am still using the original bar (Windsor with nose sprocket). I turn the bar over every time I change to the other chain.
I am not 100% sure that this practice is worthwhile, but I think it makes a lot of sense. Just an opinion.