Valve + Membrane - BelleMa Euphoria Plus

It has been two months value and membrane are out of stock.I had to spend 25$ for whole hard sheild set just to get value and membrane first time,second time around even that was out of stock and I had to buy 3d sheild set,even more expensive and terrible to use!!! If you sell pumps and advertise suggesting to replace parts every 3 months if pumping full time you should be able to keep up with the spare parts!!!!This is super frustrating!!!Is this a marketing strategy to force people to buy the whole sheild sets ???