Times are different now, COVID has changed everything, and you need to start thinking about things differently, and over the last 10 years are so our society has become more and more based around immediate gratification and disposable products.
Take phones, for example, as something that most people know won’t last more than a year or so, and yet they accept it, we no longer care about long term, we just want what the two of us want, and we want it NOW! My mom still has the old landline phone in her cabin from when I was a teenager, that thing is 26 years outdated and still works wonderful as ever.
HVAC systems are usually designed to work for a long period of time, and some of the high efficiency models can last over 15 years. The thing is, for your furnace and a/c to last that long, and work well, you need to take wonderful care of them. We aren’t used to doing this sort of thing anymore, we just throw things away and buy a modern one, however an a/c is special. You need to change the air filters, and check the ducts and air vents to make sure you aren’t getting accumulations of debris or blockages. I propose a HEPA air filter, although they cost a lot more they last for almost a full year in most cases (unless you have a lot of animals). Think long term, use your mind sensibly, and once in a while it helps to turn the AC off honestly and open up the cabin for a little natural ventilation.