Matty, your best option is ICNR, as the lights are taken, I know this doubles your imaging run but dose give you the best results, as the darks temp, is then exactly the same as the lights.
However if you don't wish to do this, try and take the darks either during your exposure run, say one every three lights, or take then at the end, but as close as possible to the temp of the lights, give or take a degree.
Leon
