First time trying, didn't know it was a switchable at first either. From the get-go, one side had issues firing.. clogged is what I figured, and some do until it heats up, but this one had problems. You would figure 6mls would last a while.. barely a week and I'm not that chronic! It gummed and clogged the air ports, seems all the glycerin burned and left the good stuff behind(looked like wax). Retailer apologised for how badly the pen worked, took it back as it was(I still had original box) and gave me a discount for my next purchase. I opted for the 8ml Planet Edition, and so far so good.
