The generally accepted info on icmag.com is 240F for 30-40 minutes, depending on how decarbed the cannabis already is (heat, storage over time) and the specific conditions during the decarb process. It seems to do the best job with all types of cannabis, regardless of whether it's THC or CBD rich.
Personally, I let the 8-12hrs of low heat in a crock pot do the decarbing. Test at 8hrs and every hour after, to find your specific sweet spot with the cannabis you're working with. :)