When an engine's piston rings and cylinder bores are worn you can get combustion gasses getting past the rings and in to the crankcase. The crankcase is the bottom part of the engine where all of the oil returns to, the crankshaft is spinning around in here connected to the pistons. This gas pressurises the crankcase and this pressure also makes it's way up through the cylinder head and in to the rocker cover - this is the aluminium top of the engine that has the yellow oil filler cap on it. This escaping combustion gas is known as 'blow by' and your engine is said to be 'breathing heavily' when this pressure is chuffing out of the oil filler cap hole when the engine is running. If your engine isn't doing the chuffing thing, then that is good news.
Even when a healthy engine is running normally there is a certain amount of pressure created, air in the sump gets hot and expands, the oil gets hot and you have pistons thrashing up and down causing displacement within the crankcase. There is a pipe from the rocker cover that goes to your air inlet pipe to relieve this small amount of pressure. With all of the heat and your crankshaft, pistons etc thrashing about, some of the oil gets atomised and creates an oily vapour. To stop this oil being carried through that vent pipe and in to your air intake, they have put in the cyclone breather to centrifuge that oil out. Any oil 'spun' out (condensed) drops out through the bottom of the cyclone via a pipe on the bottom and trickles down to join the rest of the oil in the sump.
If your engine is ok then the amount of pressure created is small and the amount of oil the cyclone has to remove is also small. As has been said above, some people just allow the vent pipe to vent to atmosphere and they plug the hole in the air induction pipe. Some people put the end of the pipe in to a 'catch can' to collect any oil that might make it through. I did the catch can thing with mine once and ran it like that for a while and got absolutely nothing in the catch can.
It's highly unlikely that you need to change your cyclone breather.