Into my fifth year with a Mitsubishi mini-split. Works great. The only ongoing maintenance is cleaning the blower fan. The HVAC company that installed the unit charges in excess of $300 to clean the blower in the inside unit. The process involves hanging large plastic bags under the unit and spraying the blower fan with a cleaning solvent.
There are several issues with this process. I believe that the blower never really gets clean, and that the process leaves a residue on the fan blades that attracts dirt.
After watching this video, I cleaned the blower myself. Start to finish in under an hour. Huge difference.
I know several of y'all are mini-split owners, so check it out: