The climate here changes the answer more than most people expect.
"Every few months" is the generic answer you'll see everywhere, and it's not wrong exactly — it's just not calibrated for Texas. Between UV exposure, cedar and oak pollen season, and hard water that spots on contact, Austin-area cars accumulate damage faster than the same car would in a milder climate.
Exterior wash: every 1-2 weeks. Not a full detail — just enough to keep dust, pollen, and road film from sitting on the paint and drying into spots, especially with Austin's roughly 250 PPM tap water.
Full interior clean: monthly. Dust, pollen, and daily use build up in carpets and vents faster than most people notice day-to-day, and steam cleaning monthly keeps it from ever becoming a deep-clean project.
Full Detail (interior + exterior): monthly to every 6 weeks. This is the cadence that actually keeps a daily driver looking consistently new, rather than swinging between "just detailed" and "overdue."
A few Central Texas specifics push the frequency up rather than down: cedar and oak pollen season (roughly December through May) coats cars in a fine yellow-green film almost daily; live oaks drop sap that bonds to paint faster in summer heat; and any car that lives outside rather than in a garage collects UV damage and dust noticeably faster than a garage-kept one.
Vehicle use matters too — a car that only does short local trips accumulates less road grime than a highway commuter, but a car parked under trees or near construction (common across the newer Hill Country subdivisions) needs more frequent attention regardless of mileage.
Booking a one-time detail every time it "starts looking dirty" tends to mean waiting too long, since a windshield or dashboard slowly fading in the sun is easy to not notice day to day. That's the actual case for the monthly maintenance club: a standing visit every month, at $100-$150 depending on vehicle size, that keeps the car ahead of Texas conditions instead of catching up to them — and any visit upgrades to a Full Detail for $40 more when it needs the deeper pass.
It's less urgent, but garage-kept cars still pick up dust and, during pollen season, whatever tracks in on a quick trip in or out. Many garage-kept clients stretch to every 6-8 weeks instead of monthly.
It makes each wash more effective and slightly more forgiving on timing, but it doesn't eliminate the need — pollen and dust still land on a coated surface, they just rinse off more easily.
Prioritize an exterior wash and wax before and after the worst of pollen season (roughly November and May) — it won't match monthly maintenance, but it addresses the two heaviest damage windows.