We have had problems on ours which resulted in us re painting the whole airframe after 5 years. Initially along seams on the wings - particularly behind the tanks where internal condensation is greatest. Then on ailerons and finally on the fuselage lap joints behind the canopy. The empennage is as good as new....
The aeroplane was finished in Mipa 2k auto paint (German), etch primed, base primed and top coated. It was a reasonable coat but not as heavy as I have seen on some aeroplanes. Personally, I would have tackled the local areas, but I was overruled by the group and one member volunteered to strip the aeroplane and had access to a professional car shop at a very advantageous price
I have seen maybe 5 or 6 cases in the UK where tin worm is starting from lap joints.
That said, all kits are different and are prepped differently.
What I am saying is the problem is coming from within the structure, not from without because the tracks start at the joint and work outwards. Those who have taken the time to fully prime mating surfaces on slow build kits will probably not be affected as we have seen on our empennage.
It isn't going to happen to all, it isn't going to particularly affect amateur painted aeroplanes, but the evidence is there. I think a relatively inexpensive application of a suitable spray corrosion inhibiter should stop it completely.
Location will be bound to affect it - we are in a warm, cold damp ish environment away from the coast but we get big temperature changes in the hangar and see condensation a lot.
Don't panic, but awareness will always help prevent an occurence and after all, we love our aeroplanes and want them to last a long time.
Our RV14 is a slow build kit and is getting fully primed on mating surfaces. It will also be sprayed with ACF50 on completion.