The O'Connor retirement was more important. Replacing Rehnquist with Rehnquist junior means that the court runs in place.
There's always the suspicion that what we don't see contains the bombshells.
President Bush was dealt a good hand that included 55 Republican senators.
There are more people who fit into the class of elderly. The more people in the group, the more cases you'll have. The problem is a lot of bad age-discrimination cases ruin it for the rest of them. You do see a number of people claiming age discrimination with little merit. It sours the courts on age-discrimination cases.
The same holds for conservative precedents. O'Connor had been critical of Roe, but when she had a potential vote to overturn it, she just partially limited it.
There is an argument that it would be appropriate now. But I doubt that will happen.
Typically, the goal is to avoid someone as ideological as [Earl] Warren or as power-hungry and pretentious as [Warren] Burger. Roberts' relatively mild-mannered demeanor may serve him well.