If coils are freezing over a bunch of time, it needs more freon... My AC unit was doing that a lot so I kept adding it, then at some point I had gone and overcharged it (it blew cold air but not as cold as I like), so ends up having to recover some until it got colder. Ideal pressure in the suction line is around 60 psi (this is where it reads 0C on the gauge) but I really don't have the means to measure "superheat" as it's a mini split.
I'm in Taiwan and R22 here is plentiful.
I work on my own AC too because the repair guys in Taiwan also charge big for any routine or small work, and I need to work on them in the middle of the night should problems develop. No AC guy is going to come in at 3AM when it's still HOT to work on your AC.