[smileysteve]

To emphasize this, recruiting costs are typically ½ to 1x 1 years salary; and you have developed knowledge.

Dollars and cents wise, I'd encourage any member to take unpaid leave before quitting to the unknown, and any leader in a growing org to accept it. (Besides in large enough orgs they have to plan for this for defense reserves, maternity, paternity, and disability anyway). The worst case scenario is that they quit when they come back, but that's still better than quitting forever today.