Reagan got three Supreme Court Justices appointed, the last one during his final year (an election year). For a good part of the country, he was the worst president ever (until W made him look like a great president). So your argument isn’t valid.
In addition, there are three other justices who will be over 80 during the next presidency. If the GOP stalls the current appointment, there is a chance that four Justices could be appointed by the next president, which totally goes against your argument.
Obama will nominate the most centrist Justice possible — despite the infamous Republican obstructionist agreement on inauguration day 2009, the President still believes in bridging the political divide. The Senate would be wise to take a known commodity rather than risk losing the Senate and White House in 2016 and getting stuck with four liberal Justices.