I just completed reading an article about a behaviorist who has been CEO at his nonprofit for some 17 years raising the question for me: when is "too long" for a nonprofit CEO and who decides: the nonprofit board or the CEO?
The traditional answer appears to be that it is up to the CEO to decide when is "too long" but I suggest that at best, it is the nonprofit board in partnership with the CEO who develop the answer to the question. Of course, the answer could be initially determined upon hiring. This is to say that were there a contract between the nonprofit board, the nonprofit's "owner", and the CEO that said that assuming good performance and achievement of agreed-upon objectives, a discussion in x years will take place to renew the agreement between the two parties.
Such an arrangement would assume that there was indeed a a) formal agreement; b) agreed-upon objectives (results-focused and measureable, perhaps consistent with a strategic plan); c) and an established periodic and formal review to understand how both the results and relationship is progressing between the two parties.
Does all this formality and the like answer the "how long" question? Partially and its a fine start. Twenty years in one institution (a not uncommon length in larger nonprofits) feels like it might be too long a time period possibly producing stagnation among other results. But many CEOs are productive and continue to be productive over this period bringing quite fine, thank you very much.
So maybe the question isn't "how long". The more appropriate question: how good?