Your math is incorrect. 3,000,000 snakes * 10 seconds / 86400 seconds in a day = 347.22 days, which is less than a year. If he was spending 3 minutes per snake

Your math is incorrect. 3,000,000 snakes * 10 seconds / 86400 seconds in a day = 347.22 days, which is less than a year. If he was spending 3 minutes per snake, 8 hours per day, every day of every year, that's 51.37 years of snake-handling, which is less than what he actually did. So, his claim may actually be plausible.