When you need to change your bag, cut off the part that is brown and sticky. Save that.
Take the bag and cook a chicken in it. It is oven safe. Really wonderful flavor. Take the valve apart and wash it in good Vodka,with the end piece from the bag The alcohol will render out all the good stuff. Make yourself a nice Martini with the Vodka while the Chicken happily cooks away in the vape bag. Cheers Dr. Bloor