don't really think bj has become a nostalgia act... it's just that they haven't been good enough to attract new generations with their music...i'll give you an example, i'm from italy and here maybe the biggest star is Vasco Rossi, who is a 67 years old rockstar that turned into a much more commercial pop act...he's just sold 6 straight sold out san siro this year and has the record for the biggest paid concert ever held (220k people) despite many of his hardcore fans really don't like his latest albums (myself included). So as you can see age is not a problem, voice isn't neither (he's absolutely nowhere near jbj's level as a vocalist and has never been), it's just a matter of bad commercial choices...BJ look like a group that has stopped being interest in selling albums and promote concerts, despite one of the biggest fan bases in the world that still follow them as you can see by how many tickets they've already sold