2hrs 2x is just cheap insurance for simple steels imo. Two one hour cycles is better than one two hour cycle. I don't think there is any measurable practical reason to do two two hour cycles.....yet I do. I guess it's to ensure you've gotten everything you can. Two one hour tempers likely accomplishes 99 percent of what two two hour tempers accomplishes.....in a custom, I don't want to leave anything on the table. Testing your process is the only way to know how well your process is working.
Not a stupid question at all, if it was a stupid question, it would have s simple answer ....it's an old question that has several answers, of which most aren't actually answers but opinions.
Of course there is an actual answer...but I don't know it. In my experience, the lead up to the temper plays a much bigger role in performance than the temper by itself...which makes comparing results of tempering among makers less than reliable.
Reaching the temp is more important than how long you hold it there, doing that twice helps a bit as well. Timing is the harder part to prove. Hit 800 for a split second on the edge and you've ruined your ht. Hit 500 for a split second.....I don't know how bad it is. Hit 450 for 5 minutes of a two hour 400 degree temper...again hard to say.
Read what you can, test what you do, you can't repeat what you read, but can repeat what you test, so you can at least be consistent.
I realize this isn't a helpful answer, but it's what a figured out asking the same question.
