So, I've been thinking about this for a while now, and I think it's at least plausible. Maybe the reason drafters have shorter lifespans is they run too much energy through their bodies?
We know drafting luxin is roughly the opposite of burning a candle to get light. However, converting energy into mass requires a LOT of energy. Getting 1 gram of a substance from energy requires 9 × 10^16 Joules, or 90 quadrillion Joules (that's 90,000,000,000,000,000 Joules, or 9 followed by 16 zeroes). Assuming the luxin spectrum is the same as the electromagnetic spectrum, with the colored luxin corresponding with the colors, sub-red with infrared, superviolet with ultraviolet, paryl with radio waves, and chi with x-rays, chi would have the highest frequency and energy, and paryl the lowest.
Drafters live to about their 40s or 50s, with women living longer than men. We know chi users have the shortest lifespan; once they start drafting, they have about 10 to 15 years to live. Drafting requires releasing the luxin through the body, almost like the body is either generating or conducting the vast amounts of energy needed to convert that energy into mass. However, as the frequency and energy of the light increases, a drafter would need fewer photons (light particles) to get the same amount of energy. So you would need less light to get 1 gram of chi luxin but more light to get 1 gram of blue luxin.
Now, I don't know about you, but I don't think the human body was made to withstand quadrillions of Joules running through it. Electromagnetic radiation, more specifically ionizing radiation, changes the human body on a molecular level, i.e. a sunburn caused by ultraviolet light or radiation sickness from gamma radiation. Imagine instead of that damage being done on the exterior of the body, the damage is on the inside.
Conducting thousands of thousands of billions of Joules inside a body that can barely withstand that same energy in smaller amounts on its exterior, it's no wonder drafters have a shorter lifespan than nondrafters.