People say vaporizer conserve weed, which they do by vaporizing it. The g pen is essentially just an electronic pipe and won't conserve your weed any better than a pipe.
If anything that pen has wasted more weed for me than saved it, I always get really shitty highs when ever I use it. you could always buy a wax cart for it and just ditch the horrible dry herb tank. I think I've used that pen to light my one hitter more than I've actually used it lol.