Running extension wires for 240v ballasts

I've got 50 ft runs between my ballasts and my lights but the lights only come with 12ft cords so I'm going to make my own extensions. My question is can I combine two lamp wires from two separate ballasts into one long wire and then at the end of the 50ft run go back into two wires? I know what wire gauge to use to stay under the amps just don't know if it will work? I'm wanting to do this because I've got 16 ballasts so I'm hoping to use 8 50ft extensions vs 16. Thank you.