To be honest I did the same until a few years ago. I don't know if milk is just more prone to going bad these days or our fridge gets open more often, but I noticed our milk wasn't lasting. No science behind it, just that we were pouring more milk away. My missus started putting the milk at the back after she did a bit of research and since then it has been fine. I didn't believe it either at first but I also did some digging and turns out the door is recommended for chilling items not preserving them.