I have anecdotal evidence - a 23 year old Honda Accord with white paint. In 1989 white paints, from Honda at least, did not have clear coats. So, the soft paint was exposed. For the majority of the 23 years I owned it I used Meguiar's in the maroon can (cleaner/wax). Also, at various times, I used more expensive waxes, multi-step processes, and clay bars. Did the multi-step processes and clay bar produce superior results? Yes. But, after 3-4 months it was the same again. The results from the Mequiar's single step was nice, shiny, and beaded water for the entire interval. I used to wax every three months when parking outside at work and then changed to six months when I got a job that provided a parking garage. The paint looked awesome in 2012 - before the accident.
Now, I use the same stuff on my 2012 Mazda 3. It provides a very nice finish that lasts a year - seriously - due to the car being "indoors" almost all the time. The product is one of the easier ones to apply and remove and it's cheap, though, not as cheap as it was in 1985 when I started using it.