25 years ago, I bought an 0360 powered Scout. It had received wing damage while operating on floats. The owner parked it outside for 3 years without touching it. The engine had 420 hours since new. I had my mechanic check compressions on the pre-buy; they were all 77/80 or better. I didn't know about cam corrosion. We repaired the wing, recovered the airplane, and I used it that summer for a fish spotting gig in Alaska; flew it 180 hours in 3 months. I noticed a little engine roughness toward the end of the summer. We did the annual, and the oil screen was full of metal. The engine was toast, I did a full overhaul at 600 hours since new...
But you can also get lucky with prolonged periods of "sitting". Later, a friend flipped his 0360 powered Scout on an Alaska beach, helicoptered it out, and didn't get around to repairing it for 4 years. It sat under a shed roof, in southcentral Alaska, without being started for the whole time. When he began the repairs to make it airworthy, I advised him to carefully look for corrosion on the cam. His mechanic pulled a cylinder and inspected the internals extensively. I guess looked great (it was 900 SMOH). It is flying now, running well.
