Many people out there that own ACs tend to get them repaired once a year or so. The main reason for them doing this is to improve the manner in which you have currently chosen to end up living your life and prevent them from having to spend the big bucks buying a brand new unit. That said, it is important to note that at some point repairing your AC is just no longer going to end up being all that viable of an issue for you to take into consideration if you are the sort of person that prioritizes financial prudence without a shadow of a doubt.
One sign that you should get your AC replaced rather than having it repaired is if the compressor stops working. Asking whether professional vs DIY aircon servicing is a good option is all about which parts of your AC are not working as well as they ideally should be. If the problem is in the coils or if you have a shortage of coolant, this is the type of thing that can be easily fixed through a professional repair technician.
Compressor problems tend to be a lot more serious though. Most professionals are going to agree that trying to get your compressor repaired probably won’t give you all that great of a result. There is a very low chance that it might get repaired at all, and even if it does you would be severely limited in terms of how long you can expect it to continue working. The expense of keeping it running would be a lot higher in the long term than just buying a new AC outright.