Not worth the money

We own a very expensive dishwasher from Siemens. It is showing an error code E15 since last November. It has been in for repairs more than 4 times. So almost 7 months without it. The machine came back last week and it is still showing E15. We also have a heat pump tumble dryer from Bosch and it also starts showing error codes E27. For now it looks like the problem got fixed, but the lint was really dirty. Shouldn't it come back clean from repairs? It is really not worth it to spend so much money on those maschines. Rather go for Miele, our washing maschine never had a problem. So what can i do now? Call the technicians again and it goes on and on till the warranty is expired? I really regret spending so much money on **** like that, could have spend it for 3 cheaper dishwasher. At least i would always have one working at home.