Rutan, I just saw a similar thing last week. An IO520 not started for 8 weeks, when started had a stuck exhaust valve. The problem was a corroded lifter. The corrosion started at an area of high wear. About 1200 TT from factory reman just 5 years ago.
On the other hand, I have recently seen an IO360, not run for 8 years and budgeted for a bulk strip prove to be absolutely corrosion free inside. Same environment too.
What this has to do with electronic ignition, I am unsure, both engines had conventional mags
Must say, I am a fan of Camguard, although neither of these engines had it in them.