YSK because the first hot spell is when most people discover their AC unit is broken.
Several years ago I waited to turn on my AC. This is how I found out about one of the busiest times for repairmen and had to sweat for two weeks. Now I do a test run a couple of weeks before it heats up. Same goes for the furnace at the end of Autumn.
Edit to add: YSK line (Rule 2)
Refrigeration tech here. Don’t run your home AC in the winter unless it was specifically designed for that. I think the person you’re responding too was assuming that because that’s what you’re supposed to do for cars that you should do it for your home too.
In cars the AC compressor runs off the belts so there is a shaft seal that can dry out and crack if the system is not run every so often. On residential AC systems the compressor is run by an electric motor that is sealed inside the compressor housing. There is no shaft seal that can fail. Running your home AC in the winter can actually damage it if your system wasn’t designed for cold weather running. When it’s cold outside liquid refrigerant will tend to condense inside the compressor. When the compressor starts in those situations it will immediately suck in and try to compress that liquid refrigerant. Unless you’re a physicist, liquids are incompressable. So you now have your compressor trying to compress something that can’t be compressed. This is not good for the compressor to put it lightly. The best case scenario here is the compressor manages to force the liquid refrigerant out adding a whole lot of premature wear in the process. The worst case scenario is that something inside the compressor goes pop and it dies.
On systems designed to run in cold weather there will be a little band heater on the compressor to keep it warm and prevent refrigerant from condensing inside it. However that is not the norm for residential AC just because most residential AC systems don’t need it and it would just be a waste of electricity.