We keep ours at 73 and change filter every 90 days. Every Oct. we have A/C and furnace checked. Probably not essential but peace of mind for us anyway.
I don't have a set time for the filter, but I write the date on the edge with a sharpie and for some reason my blower unit will start whistling when the air is restricted enough, so that's when I change it. Usually it's about a month and a half for me.
Filter every 30 days helps the life of your motors that blow the air. Staats Is usually who I have service my Furnace, air and appliances. Temp is what your comfortable with usually around 70..
I keep mine at 78 in the summer and 66 in the winter. I change my filters about every three months. I just have it serviced when something doesn't work as it should.
72, and I change the filter every month ( $0.99 ea. ) Once a year I unbolt the A-Coil ( 4 1/4 screws), you pry it up with a bar, use a small air compressor and blow the debris down into your squirrel cage, get the Shop Vac and clean the bottom. It's very easy folks! Your outside unit needs to be cleaned with a hose from the inside out. Those little pancake compressors are great!