Statements of coil longevity are baseline averages only, an average of runtimes that means some people have longer run times while others have shorter run times giving the average baseline number.
Coil Longevity Affecting Factors:
1) Biggest Killer - Sweeteners. Any and all sweeteners in a liquid are not efficiently vaporized off, they most times just crystalize and carmelize on the coil wire and in the wicking. These will begin to block the flow of liquid and leads to not only burnt and nasty tasting hits, it can lead to liquid seeping and causing what appears like leaking, sweeter the liquid the worse it gets.
2) Color of the liquid. Clearer the liquid is to pure clear color the longer the coils will last, if there is any food colorings at all, these like sweeteners will not vape off efficiently, leading to the same problems as sweeteners, dark or more color the liquid is, the worse it will be on coils
3) Flavor types. Creamy, Savory, Bakery, custardy, caramels, vanillas, tobaccos, coffees, there are many others, are notorious coil killers, these extra addatives are generally sweet, and or very dark, or creamy or yogurt types will by their very nature be coil killers due to their flavorings, and a lot of times are offenders of the above 2 factors listed above.
4) Wattage (Power) supplied to the coils vs amount of airflow. Here the wattage can play a factor, 40watts may not sound like a lot of power, but about 60% of real vapers are below 40watts. The TFV4 line of tanks were generally pretty airy to begin with so watts really do not affect them that bad as other tanks. Still, if you are running into clogging issues due to one or couple of the above 3 factors, if the wicking gets dry and there is a lot of power and heat at the coils, that dry wicking can begin to burn prematurely. However being the coils are SS316L and fused claptons, they need to much power to begin with due to wire mass so, my exposure to prebuilt coils with claptons and fused claptons, they don't last long due to the issue of them needing to much power and heat to function right, but not enough wicking flow in their design to counter-balance the needed power, so thus they burn out faster than a standard coil head.
Next issue will be with your ordered KBox200, which is a safety issue regarding the batteries. Be cautious what batteries you get for it, the link in my signature line has a break down of the highest suggested batteries and safest batteries available currently as well as what battery for what battery configuration the max wattage ratings. Being a dual battery mod, the three best batteries are as follows
If you do not see yourself going above 120watts - so 120watts and below, the Samsung 30Q 3000mah 20amp CDR
150 to 160watts and below - Sony VTC5A 2500mah 25amp CDR
180 watts and below - LG HB2, HB4, HB6 1500mah 30amp CDR <=Do not trust any battery that says on its label that it is higher than this amp rating, there is no such true animal, no 18650 battery rated for higher than 30amp continuous discharge, other batteries claiming 35 or 40 amps, that is a short pulse discharge rate (generally 1/2 to 2 second short pulse, after which the battery needs to shift down to CDR or overheat and vent or explode), no getting around this limiter in the 18650 form factor.