So, I finally got my Astaroth supporter to +15! This is my first +15 supporter and they made me suffer for it, lol. I do not recommend pushing any support to past +10 unless you have a TON of materials to burn or really like the supporter as the material cost alone just isn't worth it when there are so many supports you can enchant with all the materials you will burn. There are a couple more I might take to +15, but i'll probably hold off for a bit.
Shin Ein currently has 22,567 views spread across 148 videos for Action Taimanin. His channel currently has around hours worth of content for Action Taimanin, or 48.15% of the total watchable video on Shin Ein's YouTube channel.