Indeed, i store the bottles in a cupboard, so it's just exposed to light when i am developing rolls.
Thanks for all your advise. I will try to by another quart of diafine, in case i need to increase the volume.
I am quite happy because i think i found my dev for my practice. And most important, i was looking for a product which can rest for a very long time. It fits with my availability for my photo practise.