When you think of the grief and suffering that they must have caused to so many people, two years prison is way too short a time. Castration with a rusty, blunt saw is far more appropriate IMHO.
We had a postman with similar propensities. One day, whilst under the influence of cannabis, he rode his bicycle into the path of an oncoming bus O. When the police opened his home up, they found cupboards full of undelivered mail going back for many years.
The strange thing is that almost everyone suspected what he was doing but nobody took any action because he was such a nice guy.