I know that there are a ton of threads about this around the web, but I haven't been able to find an answer to my specific issue. I have been very diligent with my battery care (never charged over 2C, never left charged for more than a day) over the years and still have all of my original 3 year old freefly 9000mAh 6s batteries performing nearly to the second for flight time. I mainly use my 10000mAh tattu 6s batteries, but ill use the freeflys if I need to get a few more flights while resting the tattus after flying. Just last week the batteries started t get a very small amount swollen, almost not enough to see, but you can feel it. When I charge them on either my 308 Duo or hyperion 720i, I can see that my resistance of each cell is very low, somewhere around 1.5-4 per cell when looking at the 308, total of 12-16 total on the hyperion. I had always thought that you had a pretty good indicator of battery health from seeing the resistance, but the fact that the packs are swelling a bit tells me otherwise. What have others experienced?