I have a 2012 outback 2.5 in NEPA with 125k miles. Lots of salt here. What I've been doing is as I tear into stuff I take a wire wheel on an angle grinder and or a drill, and a needle scaler for tight spots and I remove all the rust I can get to as best I can, then I clean it really thoroughly finishing with acetone. Then I spray a rust converting primer on it. Then I spray a couple light coats of undercoat on it. I did the drivetrain fluids and timing belt so I had it kind of apart in the spring and did the whole front end.
I did a lot of the rear end last year when I did the struts and brakes. I pulled the muffler and cleaned out around there as well. I will be going back and getting the spots I missed. It only adds an hour or two to whatever else you're doing. I even hit any little bubbling I see on the body paint. I've done this on other vehicles and it holds up very well.
I also clean the undercarriage with a pressure washer in the fall, then allow it to dry. Then I will pull my skid plate, do an oil change, and coat the whole undercarriage in Fluid Film. I got almost all of it with 2 cans, three would be better especially getting the nooks and crannies. Throughout the winter I will also rinse the car off with my house at the house as soon as I can after a snow event. I hate seeing the salt caked on my car. The rinsing doesn't seem to affect the fluid film, I was under my Outback today and it still had a healthy coating of oil under everything.
I estimate I put like 2-4 hours a year into stripping, treating, and painting rust as it is done when I have things disassembled working on other stuff. Then about 2 hours to wash and coat with fluid film, then perhaps a total of 2 hours rinsing it total over the winter. So eight hours of work in a year and my car looks cleaner than any 5 year old car around here. I hope to drive this car a long time I'm quite fond of it.