Would expanding my ears to 4mm be reversible (to an extent)?

I have stretched my ears to 3mm twice before. They have shrunk down both times. I only had them in for like a year tops really but yeah. I asked my piercing studio when I did and they said normally you can go up to 5mm with them shrinking back no problem. Its when you go larger that its an issue. You seem quite responsible about it, going slowly so i'm sure you will be fine :) I know people who don't want to wait and go slowly and they have resulted in stretch marks on their ears and one guy even had the lower part of his lobe rot and he had to get it cut off and stitched up. The thought of that happening makes me always go slowly lol Good luck! :)