I've had the VTC for quiet some time now but only using temp mode for a month. In that time it only asked me 2x if I have new or old coil, yet I do change coils. Also the resistance locking doesn't seem to do much of anything. Locked or not , it vapes the same and even when locked, the resistance can still change from say 0.13 to 0.14 ohm as coil gets older. Like I said, it vapes great so I wonder if anyone figured that out.