I would love to be wrong, I was a huge YiHi support and DNA hater. I have unforgettably learned the hard way. As time goes by your mod will get hotter and hotter. You hold both + & - to lock resistance while in temp control mode. The coil must be room temp or you will not get a good vape and you could even get a short. At first it should lock right away to the proper ohms but overtime u will notice it jumping, for instance if its suppose to be .25, it might show .12, .15, .44, .82, .22, .55 if you click the lock command in quick succession. At this point your mod is shot. Any coils will get messed up and melt out of spaced formation. OCC coils will pop. Even power mode will be unreliable. You will notice extreme heat coming from the USB port area where the bottom of the chip sits inside the enclosure. After a few days the internal mod will melt and it will possibly explode, as some peoples on reddit's batteries vented from the heat.
You should get about 3-5 months of good vaping, be aware of the signs and take proactive action to get it fixed or get a new mod for your own safety. Never use unpaired batteries as well as this will accelerate the decline, as a friend did that and after a few days his mod melted. Hopefully by then Yihi will have kicked there game up and you can get in something more reliable rivaling the features of the DNA 200, at 1/4 the cost. Or maybe by then prices will be lower on them. Good Luck
EDIT: I had mine since Aug as well, My wife also had a IPV4S and hers failed in the same way in 2 months. All this info is to help you be aware of the issues from someone who experienced them and make sure you know the signs and risks
