Why is the assumption that senior faculty are unproductive?!! I'm starting to resent this implication/assumption. I'm a senior faculty member, not quite 50, I publish actively (typically about 5 articles/year, plus chapters in books, etc), I sit on an NIH panel, I'm on my field's publication board, I mentor junior faculty, teach, have 2 active NIH grants, one under review, and two about to be submitted. I currently have 5 doctoral students, two post docs, and a slew of other folks who work in my lab (all supported by grants I've written). I teach, serve on committees at the local and national levels.
At the same time, I'm starting to care less about the department and the curriculum, etc. My raise last year was a paltry 3,500-- to get time off teaching I have to write more grants. How about a course off for what I've already done? Am I bitter-- not yet, but I could get there in a hurry. There are people in my department who do less, have no students, no grants, minimal publications each year and have the same courseload. What might revitalize me is rewarding productivity more than time (barely) served.
In my comment above, I was targeting that group. If you are earlier in your career it is possible to rescue you, but truthfully, if someone is a lazy do-nothing at an early age it would better to bring them up for post-tenure review and dump them in this situation!