I don't trust the old "go with a reputable breeder" alone when it comes to hets. I've recently seen some discussion about hets from reputable breeders NOT proving out and the reputable breeders blaming that on their employees switching snakes around.
Which can turn into a mess of finger pointing.
I would only consider buying hets from a breeder that is not only reputable, but that has a bombproof way of guaranteeing them. Example, microchipping some snakes. Pictures !!! Pictures of the adult on eggs, marking the eggs right away, pictures of snakes coming out of the eggs, good quality pictures of hatchlings from different angles. Paperwork with pictures, or chip numbers, etc etc. Good written guarantee based on the foolproof system.
I would want more then just reputation. I would want an actual system in place. As fool proof as possible. Definitely more then "marked tubs".
Nothing more disappointing then buying hets, raising them up, finally being able to breed them and ...they don't proof out. Then waiting a year, breeding them AGAIN to make "sure" and again, nothing.