Marlin I may not have the terminology that you do because I have not been formally trained.
I do learn proportionally more from my mistakes then anything else and just hope that they weren't expensive mistakes on irreplaceable items.
I have learned much of this through necessity and the failure of others that I relied on and am the better for it as a result.
I ultimately have to fix their mistakes.
Doing my own valves also lets me get the width of the seats where I want them. I find that the thin "drag race" seats offer the most improvement. For me that doesn't matter so much since I don't put many miles on them anyway and can always redo them if necessary.
I was pleasantly surprised how detailing the seats gives so noticeably increased pep to the engine. It adds crispness to the throttle amazingly.