The fact is, you can never replace a long-term person, and ironically, that's usually a good thing. Here's why: Over the years, the employee has surreptitiously created a unique job, regardless of what best suited the firm. Everybody does it. For example, the technically oriented person adds technical responsibilities and off-loads nontechnical, and the social engineer goes after more people-oriented responsibilities, until each has dumped the work that was not appealing.

Because it evolved quietly over the years, no one noticed. Now the new person comes on and tries to fit into a job that suited the previous occupant and no one else! The new person has different interests and abilities, and wants the job to conform with those. To compound the problem, the new person doesn't have the personal relationships with the rest of the staff the predecessor had, so the new person fails.