?? Much was painted in the first place. The rest, paint doesn't last.Why use all the oily underside treatments? Hard to clean off and collects dirt. Just clean and paint it like it should have been in the first place. After a good paint job and it cures then apply the oily where needed.
If you want to keep a car or truck in nice shape. Only scenic drives on nice days other wise don't use it.
How many here wish they had the means in the day to buy some new vehicles and just put em in a huge sealed box.
How much would a brand new perfect with window sticker 1957 chevrolet car, or pick your what ever from those days go for now?
Do you really have much experience painting the underside of vehicles, the prep work and actually doing it? Unless it's a frame off restoration on a classic with a frame, it is not that simple.
What does it matter if it collects dirt? It's a tiny itty bitty bit.
Yes, one important variable is plan your trips. If you take it out in weather that promotes corrosion, corrosion you shall receive. If you work a daily job where you have to commute, it is what it is. If you don't, or pick one of your vehicles to save from that exposure, it'll last a lot longer before rust takes its toll. Been there, do that.