well they must put the screw thread on for a reason may be to f up post like this lol.
No lop not the main cause for head failure at the end of the screw thread age is the main reason they fail at that point. Don't see first and second life units cracking .Generally older ones that being used past there expiry date on o/h cause the owners never got any coin. I know one operator never had any problems never lop at all but he change his cylinder's after 2 lifes never had problems. Cold morning and people that don't warm there engine up before take off, we preheated oil and engine in the colder months as I said before we never had much of a problem.