Came up with a couple more possibilities:

9. Took a vacation (but who's going to check his mail box for mail throughout the day?)
10. Went to Mannix family reunion(same as above)
11. He realized with his advancing age that he's no longer be able to google people's pi as well as he used to so he retired
12. Finally realized how fucked up it is for a 60 something year old man to pretend he's a 15 year old while using people's personal info to harrass them on the internet and irl

I'm leaning towards broken computer.