User blog comment:Nmrls/What are you looking forward too?/@comment-5068504-20130105230126/@comment-432124-20130108030117

According to Greg, Superman is only slightly aging slower than normal humans, which means that he might not be as long-lived as you think.

As for Superboy, if he's aging internally but not externally, that would have to mean that his internal cells are multiplying faster than his external cells. And mind you, his DNA was constructed and spliced together by Earth scientists who had very little knowledge about Kryptonian DNA or about how combining it with human DNA would affect him. So if his aging condition is a side effect, there could be other side effects that haven't been disclosed as of yet.

But either way, I'm pretty sure that his days are numbered, considering that everyone else's days seem to be numbered this season.