I use this type of product also, though I'm not sure of the brand.
To those that don't believe it can last a year, it's absolutely true.
Now here's the really interesting part, from my experience, take it as you will.
Ever since I started using this instead of conventional anti-precipitants, my girlfriend can't stop talking about how good I smell. I mean she absolutely LOVES it, and it's not like cologne, I don't really 'smell' like anything, but there's something there.
My own theory is pheromones. They're usually released from sweat so normal antiperspirants stop it. However with the crystal stuff, you get the benefit of pheromones, but no BO since it kills the bacteria.
Highly recommended, to save a crap load of money if nothing else.