Question for those who have used Speedmaster assembled heads or valve springs

I run at least 140 lbs on my Street Cars that have solids and 350 lbs open
with no issues for the last 60 years. More on my Race Cars than that.
However, I do NOT let my car idle for any extended period of time ever =
Just shut them off if more than a minute or two.
However, I use quality CWC cast camshafts and not the new Chinese junk!