I was curious, so I looked around on WP and a few other sources to answer a question.
With GHWB's death, there are now only four former living presidents and the current office "holder". During my 51+ years on this planet, there was a 564-day stretch where there were no former living Presidents. The irony about this period is that it began with the death of the person who was President when I was born (Lyndon Johnson, January 22, 1973), and ended when Nixon climbed the stairs into the helicopter on August 9, 1974.
It makes me think Nixon was truly alone during the end times of Watergate. Not that it obviates him from his actions, but having someone to talk to who had similar experiences might have helped.
Of course, the only two former presidents immediately beforehand were both Democrats, whom he probably wouldn't have listened to, so there's that.