New Edy heads, poor quality control what to do

I bought my Eddy's in 2000 new. I left them in the box until 2006.
my machinist checked them over & didn't find any concerns.
Bolted them on a cheapo short blk, & it ran well.
2007 I built a new short block & changed the valve springs to match the cam.
Set the spring hieghts & did nothing else to them.
They have been on this short block since 2007, starting my 6th season of racing with them.
Maybe the older ones had better quality control.