I'm a bit different than many people here because I don't spend $thousands on ceramic coatings, wraps, clear bras and other add-ons. I take a brand new car, prep the surface as needed (minimal if any clay bar), then wax with a good carnuba/polymer paste wax. All my washes are "as needed" which varies from a couple of days to a couple of weeks in winter. All my washes are using the same brand of lubricating soap as the brand of wax I am using. I wash using an ordinary hose nozzle and a well soaped lamb's wool mitt, strip water with a chamois and dry with a micro fiber towel(s). I'm currently using Mcguires Gold Class carnuba/poly on the Stinger but had outstanding results with Black Magic on my 13-year old GTO which still looks like new.
I've found that the secret is to keep the surface clean as often as possible to prevent accumulation of tree sap, grit, dust and industrial pollutants. Hand washing does that, pressure washing does not. Insects are especially bad at etching the paint on the front of the car and keeping that surface clean and waxed is essential. Rock chips I touch up after every wash job if needed. I use touchup paint from Automotive Touchup which has been a perfect match on all my cars, dry brush the color in and clear coat to prevent erosion around the chip area. I try to wax every 3 months long before it is really "needed." That keeps the surface covered before the wax is "used up."
Short answer -- every 3 months, maybe longer in the winter depending on ambient temperatures, and whenever I feel like it the rest of the year.