I agree.
That first day, as soon as I heard that is what she did, I raised my eyebrows in surprise, but wasn't really sure whether that was some type of general practice for the USSC retirements.
Now, I'm pretty sure that it has not been.
This is a dangerous way to operate, I'm afraid. As you point out, it makes it tougher to get serious about finding a replacement. That, in addition to my point about "Suppose O'Conner decided she didn't like the person confirmed (or about to be confirmed) and withdrew her retirement" scenerio - this really seems like asking for trouble down the road.
If that occurred, what would be the alternative? Impeach the justice? Supposing something like a 55-45 vote on the replacement, there are 45 primed to vote against impeachment - it would be a real pickle, I think, especially if a majority of the USSC justices were to agree with the rogue.
"I do not like this, not one little bit."
I don't see any of those nightmare scenarios happening. But what her "hanging on" does do is reinforce the false premise that there is some duty to preserve status quo ante of the balance or makeup of the SCOTUS. That each nominee should mirror the philosophy of his or her predecessor.
Lots of that sort of talk going on, and will continue. Schumer said outright, "Alito is not in the mold of O'Connor," and uses that as a springboard for his preliminary objection. "A divider, not a uniter" is the same sentiment in less personal terms.