You’ll know your Yocan vape is empty when you can see there is no more oil in it, you struggle to produce vapor, and the taste of the vapor deteriorates.
When should I stop hitting a THC cart? When the oil is mostly gone, and you are no longer getting a decent “hit” off of your pen. Most cartridges are clear enough for you to see the oil. Disclaimer: THC oil cartridges are suitable for vaping and are not the same thing as tinctures, which are for oral use only. You’ll know when it stops giving a hit.
What happens if you smoke an empty cartridge? Vaping an empty cartridge or tank will create smoke, but it has a high chance of burning your mouth and possibly your lungs since the coil has nothing to draw from besides itself. I would highly advise against doing this as it will hurt and taste terrible- like metallic kind of terrible.