I have a Toyota Corolla 1999 CE, with 199,000 Km, I am the original owner, no rust.
This is what works for me.
I wash my car 1 to 2 times every 2 weeks in winter (if you live in a city that uses alot of salt), and 1 time a month in summer. (more if it gets dirty quick0 I wax 3 times a year.
If you ask me rustproofing is great if you want to throw away money. In any case the galvanizing, paint and clear-coat should be sufficient provided you touchup nicks and wax, wax, wax.
BLB555