I have to vouch for the effectiveness of a adenectomy. If done by a veterinarian the chances of the snake becoming venomous again are superbly minimal. Testicles don't grow back after a neuter. Neither do ovaries, eyeballs, and other amputations.

Increasing the odds of regrowth would be a ductectomy (leaving the gland in place), and species where the gland is so involved with other facial structures that 100% removal cannot be garanteed. In my opinino a vet should give out a certificate of devenomization just as he/she gives out neuter certificates. They never say that your dog is 99% spayed/neutered do they? Because this procedure isn't routinely done the vet organization does not require such certificates.