I had a pair of heads, and a spare set of NPR 1700 slip in 96's, stored for years il L.A.
I kept the heads, but gave away the pistons and cylinders, because I KNEW that I'd never need them! (The Big 4 rebuild is a couple of years away.)

I just pulled the heads to change them over, and found a 40mm crack in one cylinder.

It was all going too well...