[KTL]

You got lucky that you didn't break any of them. If you're not going to torch the remaining nuts off (cherry red with the ox-acetylene "blue wrench"), i'd consider cutting them and trying to split them instead of relying on the penetrating lube.

I agree with the periodic removal approach. Once I got mine off, cleaned the threads and used a good dose of anti-seize, I have since made it a point to crack the nuts loose and re-tighten on occasion. I was lucky with my car that it's a rust free car with little foul weather use and even mine were tough to get off. Other friends with much more weathering were not as lucky and had to drill out broken studs.

We're fortunate nowadays with the nice drilling jigs that some of the contributors on this board joined in to make and sell to a wider audience via Pelican. A drill jig makes the repair a lot less painful and nearly always avoids the need to use a thread-sert or helicoil. I believe it was John Walker and A Quiet Boom who got together (amongst other people i'm forgetting) and perfected the drill jig for all the 911 port sizes.