Yeah, I was thinking it would be intended to be permanent -- Wrathion wouldn't know what's going to happen so his game plan would be 'attach this to her in a way it won't come off, so she can go fly away and still have the ward running'.

Since she's staying, however, he can always top it up and adjust it while he's with her. I think, logically, he might try and attach it as a band around one of her horns. Not much feeling there if he clasps something around it and secures it, and its physically close to her actual head/mind and all since she's... large... so you want it to be strongest there from his perspective.

Horn decoration is very normal for Azeroth dragons... ITS FASHIONABLE, IRENIA, AND ALSO PRACTICAL? He'll put little sparkly gems in the shiny band...