I think the true answer to this question is, "it varies". Many of the different high CBD strains are sativa hybrids which are going to reach their peak level of CBD at different times and that takes lab testing to confirm with any real accuracy.
In general the answer is "earlier is better" though. Because the moment a cannabis plant produces CBD it immediately starts degrading into CBN and THC, so any extra time waited after the plant stops making CBD just means more CBD being lost unnecessarily.
In general the answer is "earlier is better" though. Because the moment a cannabis plant produces CBD it immediately starts degrading into CBN and THC, so any extra time waited after the plant stops making CBD just means more CBD being lost unnecessarily.