I agree. Beiber was a boy wonder. If he remained the boy next door, he would've become irrelevant in a year or two. Becoming the public enemy is probably adding a decade or so to his fame as the male version of Lindsay Lohan.
And I agree about Timberlake. I was in middle school when N'Sync came out and I didn't think they would last. Then Timberlake transitioned into a solo artist and I didn't think he would last either. Then he become versatile musically and started getting into hip hop and pop. I'm definitely not a fan of his music, but I have to give him credit for his acting ability. Very surprised to see how natural of an actor he is. Kinda reminds me of a young Will Smith or Mark Wahlberg. I can see him becoming a respected actor (by the academy) in a decade.