That sounds like a person that doesn't know what kind of animals he's working with. Please avoid doing business with these kind of people...
According to one of my books (Necas, Chameleons: nature's hidden jewels), montium can live about 9 years.
I think it's not smart to buy WC montium anyway. The wild population is declining and listed as Near Threatened, they have a small range in which they occur in the wild, habitat destruction causes the population to be fragmented, and they're under pressure due to overcollecting for the pet trade.