Do you have a dash cam or any other accessory fitted that might continue to draw power from the battery when you’re not using the car? What type of journeys are you travelling and how often do you use your car? If your car is used infrequently and on predominately short journeys, those two conditions aren’t the best for good battery health.
You may ultimately need to get the cause of your battery drain checked out to avoid having to keep replacing the battery, which is likely to cost more than paying someone to investigate and determine the cause of the problem. If you don’t want to pay main dealer prices, you could always go to a good independent VW specialist or a specialist auto-electrician, which might be cheaper.