There's no single answer that fits every home, but a practical starting point for most Hawaii households is a professional check-up once or twice a year, timed around the seasons when the system sees the most use.
Two factors push that interval shorter here than in milder, drier climates. High humidity encourages mold and mildew buildup around coils and drainage lines, and salt-laden air near the coast accelerates corrosion on outdoor components.
Between professional visits, a simple filter check every month or two goes a long way — a dirty filter is the single most common cause of reduced cooling performance, and it's the easiest thing for a homeowner to inspect without any special tools.
If a unit runs almost continuously, sits near the ocean, or is more than a few years old, leaning toward the more frequent end of that schedule is generally the safer choice.