No way can he sustain the attention beyond his 30's. His demo will grow up and he'll eventually be a creepy old guy the next generation isn't interested in.
Many celebrities and entertainers can bring their fanbase with them as they get older. This is literally what people like Leno and the Rolling Stones do.
There will always be new children who will go to youtube and find the most popular youtuber...unless he gets burnt out or feels he has enough money, he's going to keep raking it in.
