You'd like to be able to hire a new employee as quickly as possible, but you'd like departing employees to hang around as long as possible. That seems to me to

You'd like to be able to hire a new employee as quickly as possible, but you'd like departing employees to hang around as long as possible. That seems to me to be a fundamental conflict. New employees don't appear from a vacuum and old employees don't disappear into one. Other than new entrants to the market and retirees, almost everyone is moving from one place to another, with the same pressures. Given that companies usually only hire when they already need the staff, there's likely a fairly strong incentive to encourage the new hire to move to the new job as quickly as possible. As someone one the receiving end of that, it sucks. But now, facing the other end of the hiring game, I'll bet you're going to encourage your new hire to start ASAP (in fact, giving preference to those that can start sooner rather than later). It's like the passing around of electron holes.