From my experience as having been an Elder is that there basically two kinds of Elders. [Eventually] a split develops (due to the person's base personality) where you begin to love the attention of the congregation and the fact your voice has authority, or you become an Elder just happy to work for the Brothers. The first group very quickly learn how to pass of the more mundane assignments to the second group. The glory seekers are normally happy to do public talks or the Watchtower study but are often absent on work based committees and midweek field service groups. As a result the glory hunters never step down from the body of Elders. Why? Because life is good for them.
I recall a "very prominent" elder in my Cong asking for the other elders to give him some relief from his mundane duties because he had been assigned TWO talks at the Dist Conv. and was overwhelmed.
I asked why he accepted TWO assignments if he wasn't going to be able to handle the additional responsibility and suggested maybe he should have been humble enough to realize his limitations and that one of those talks could likely have been handled by another elder who got NO speaking parts on the convention. Or did he think that NO ONE ELSE could do it as well as he could?
He said he certainly was not so arrogant as to think that, but evidently the CO making the assignments did.