Keeping your blast nozzle in good codition keeps your blasting production at it's most efficient. Once the noozle wears the orifice ghets bigger and the blasting impact drops slowing down productivity.
A good tip to check you nozzle orifice size is to use a drill bit of the same size and insert into the orifice. If it's a reasonably snug fit your Nozzle is not worn. If the nozzle orifice is quite a bit bigger than the drill bit then it's time to change the nozzle over.
A new nozzle is like a good tune up for your sandblasting machine. You'll notice the difference right away.
Here is John-Anthony from Rayzist talking all things Nozzle.