How often are you refilling? Here's what I recommend:
1. Let the unit rest when the atomizer tube gets any warmer than luke warm to the touch.
2. When breaking in a brand new atomizer, drip 5-6 drops on the atomizer, then 4-5 after every 4 puffs or so. As soon as you notice a change in flavor, redrip.
3. Blow out atomizers regularly, and allow them to drain over night.
4. Be sure not to screw the atomizers onto the unit too tightly, as this will push in the contact points at the bottom of the atomizer, and cause it to short out your entire unit.
5. Do not depress the button for more then 2-3 seconds on the 901 or 510 atomizer, or 4-5 seconds on the 801. You can continue to draw in after releasing the button, but holding it down for any longer than that could result in popping the atomizer.