I've been with Danse for an extremely long period of time, way longer than any other companion. I do everything this dude likes, I stop doing drugs, I take him on a lot of Vertibird rides. He's with me when I help settlements, I jump in and out power randomly to get a like from him. He just loves when mod a legendary weapon a certain sometimes, it depends and he loves when you mod legendary power, for example the chest from the Captain of Prydwen and the chest Cambridge labs. I've had three conversations with him about his past and now it's been almost two months in game time and nothing from him, I'm debating on taking him with me thru relay to the institute and I'm working with the minute man to reach the institute, but at this point I'm ready to ditch Danse. I should have had his perk by now.

You only get his perk after completing blind betrayal with him alive.

You can only get his personal quest after going through BoS quests long enough. You can't max him out before then.