Doesnt matter how much time he gets...its pointless. When he gets out, he will still prey on kids...until he dies.
It's sick shit and I want these people to die too. But Germany has been doing some interesting stuff attempting a different approach in rehabilitation, I'd like to see their results some years down the road, it could be useful and necessary at some point because the reality is most pedophiles aren't getting 15 years and many never even go to jail and the ones that do, like you said go right back to doing what they were doing before. I'll post some of the interesting stuff Germany is doing later, honestly makes me sick researching this kind of shit though.