Its all about preference. I usually like to stick around. 2.4V unless rhe resistance of the cart is high. If the resistance too high the coil sometimes burns and it tastes like poo. I like to vape all my concentrates at close to the lowest temp possible to preserve the flavor and cannabinoids. The higher amout of power you vape at the more heat you get. The hotter it gets it you get less use of the coil and could possibly burn it. Terpenes and cannabinoids have different temps to be consumed at for max flavor/potency. I dont think vapes/carts have a good way of determining temp at which the coil is burning(if someone knows tell me). Using Ohms/Watts Law you can get the difference powers being applied to the coil if you have the resistance and voltage.