Also one of my favourites!
Regarding her vocals...
Yeah, all voices change over the course of a lifetime, some more, some less. And it also depends on the day, the overall lifestyle and outside conditions.
Kuu's voice already changed once between her debut and her peak, loosing the rawness.
Apart from that her workload did have the effect that her voice gets tired more easily at the moment, but I hope that will get better again with time.
So some performances are great, some not so much right now.
As I already mentioned her stage fright seems to have gotten bigger in recent years as well.
The thing she said after the XXKK performance when they cut out? She said: "I was so nervous" again.
Guess all the negative stuff within her career didn't leave without a trace.
I'm just happy that I still like how she sounds after 20 years.