I'm on my third Crafty. I abused the first 2 using with friends like a joint, always at the highest temperature. This one I have is out of warranty so I'm babysitting it. Changing the battery out of a new +20% Crafty is a waste of time and money. You should do it when you notice a drop in functionality. If you use it, or abuse it, you will notice it doing less and less bowls with a charge over time. You start with 5 and after use it becomes 4, then 3. Then 2. Changing battery has to be done after this process has taken place. Thermal fuse and battery are a problem if you only have this vape and want to achieve group use, connect it with glass and using it 100% of the time at its maximum temperature. Doing so you will need to send it in sooner or later, or mod it yourself when the warranty expires. If you plan to use it A LOT, get a Mighty or even better a Plenty who doesn't rely on battery and will last you many years.