According to the Wall Street Journal[1], the government would probably have asked for 7 years, and a plea bargain offer was made to reduce to 6-8 months in prison. The 35+ years was the potential maximum, would have required conviction on all charges, and ultimately would have required an independent trial judge to "throw the book at him."

[1] http://online.wsj.com/article_email/SB1000142412788732458150...

And "checking out too many books at once" = allegedly hacking into a third party network to download 4 million articles from 1,000 academic journals without paying the required fees.

Not to mention bankrupting himself and his family if he had mounted a legal defense against the charges...