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This is just my opinion and yous may question it but I feel its a pretty good theory. Considering winter cooling actually promotes viable sperm in males,would yous not agree that the earlier in life you cool the younger they may breed or more viable there sperm may be? This is just a theory of mine and there is no harm in trying it.
I do not cool them for their first 12 months but every year after that I do.
With diamonds I suggest you DEFFINATELY DO cool after 12 months of age and every year there after as I have heard that males that wernt cooled as juveniles had become sterile at an older age (This may be true if they were not cooled untill 3-4yrs)
Also DPS can be linked to not cooling your diamonds as suggested.

As for cooling with majority of species I just gradually reduce temps to 18-20 degree night time temp over about a week period. But with diamonds I would house them in foam shipping boxes in a garage for 2 months or so. Temps are approx 10-16* (Id try and stay between them temps roughly 12-13*)

Also I dont feed at this time and give them a constant supply of fresh water

PS I have never kept diamonds as of yet but intend to soon.I have read during winter temps range between 0-16* but I would be too scared to totally hibernate my snakes so I suggested roughly 13* (dunno if that will work or not I am yet to find out).

Also sorry for modifying my post here but wanted to make it clear I am just using my opinion only that may or may not be correct.