Long term running at WOT will definitely shorten engine life. I rarely run mine
at WOT and then only for a few minutes at best. My max RPM are 4800 and I never
cruise at more than 3600 unless I am trying to outrun a storm to safe harbor
then I will up the ante.

Also, after any long cruise it is best to let the engine idle for 5 minutes or
so to cool down from the run. I do that and it seems to work. If I shut right
down from a hard run mine will diesel sometimes too.

If quitters never win, and winners never quit, then who is the fool who said,
"Quit while you're ahead?"