I've only been to one, sadly.. Even though I'm very thankful that I was able to go!
I went to see ToppDogg in London in 2015, and I swear it was the best concert I've ever been to! I don't actually live in England, so I had to fly over there to go to the concert/showcase. I saved up for a long time, got a good ticket + cheap ass plane tickets, haha, and I really enjoyed everything. ToppDogg means a lot to me, and I'll do anything in my power to support them! I got to meet OT12, sadly no Seogoong, but not long after the concert the group lost two members, and after that they lost another one... Now they're OT9, with one member being in Produce101 s.2, so I really don't know how their future will turn out :/
I'm thankful that I got to meet so many of the members, and I wish them the best in the future. May all the luck be in their favor!