That would have been in 2013-2014. Now it is known that the Republicans took the Senate majority at the end of ’14 - and that Trump won in Nov 2016 and Republicans held onto the Senate majority in that election.Harry Reid installed the “Reid Rule” in the 112th Congress to prevent Republicans from filibustering the confirmation of "Obama judges” (as Trump styles them) and enabled the Democrats to pack the First Circuit in DC. That nominally did not include SCOTUS nominees - but everyone understood that if a SCOTUS vacancy actually came up, extension of the Reid Rule to cover that contingency was a foregone conclusion.
The point is that the Reid Rule was a bet that the Democrats were going to keep the Senate majority into the indefinite future. If Harry Reid was that willing to put his chips on the table betting that the Republicans had no chance of taking the Senate and the WH, he certainly had no rationale for pressing leftist SCOTUS justices to hedge his bet by making a career-ending decision to retire.
Back when Harry was instituting his rule, you and I would have been thrilled out of our minds to know that the next two people to be elevated to SCOTUS would not be nominated by a Democrat. Hindsight is wonderful, but RBG was far from the only person to believe that she would definitely be succeeded by a Democrat whether or not she retired before 2015.
BTTT.