curious about valve lash setting/check

I've always "been told" that you "want" the lifter about in the middle of it's travel with valves closed. "This might vary" from lifter brand to lifter brand, or, LOL with the incredible deck/ head precision to which these girls are born, from one lifter position to another. Bear in mind that thousands of these were built WITH NON ADJUSTABLE lifters, and ran many many miles, some quite hi performance LOL