I did 1.5mm every week until month 3-4 if i remember correctly. After that every 2 weeks for another fews months, then every 3 weeks. I don't bleed, but that's probably because I don't push down too much. Redness is all I go for. I've been needling for like year now. Hair feels super strong and healthy. I have progress pics from several months ago on my phone that broke down, but I am sure there has been great improvement since then. Hair felt so sh*t pre-needling. I have posted some pictures here in the past, but I'll do another comparison soon.
Reason I don't do it too often is because I still have flaking, sometimes even after 2 weeks, so I feel 3 weeks is good, just to let the skin heal. Besides, I am planning to keep doing it and I really don't think doing it at deep length too often can be good, but who knows really. We all gotta try for ourselves until Follica comes out or something and gives us a better understanding.