When I was first out of my parent’s house, I lived in a large house with a pool with 4 other roommates. Some were in college, some worked, and we rotated roommates every year or so. It was a great place to live, but we did very little to take care of the house. The owners took care of everything for us like a landscape service and pool service. We all pretty much assumed that was all there was to taking care of the house, and if we needed anything else we just called the owners. During the summer one year, the air conditioning stopped working. It was really hot and miserable and we called the owner right away. They sent out an HVAC tech who checked everything out very thoroughly. He pulled out the filter for the system, and honestly it was the first time I had ever seen it. It was full of pounds of dirt and dust and spilled all over the floor when he brought it out. He asked when was the last time we changed it, and I told him “never”. He was nice about it, but kind of shook his head. The thermostat needed new batteries and the refrigerant was low. Once he fixed everything, we all noticed the AC was better than ever. He called the owner when he was all done and suggested they have a service agreement with him so he could check the system every 6 months. He also left several filters for us and said we needed to change it every 6 months. We all enjoyed the new, great working AC so much, we made sure to change the filter, but that was the only reason.