On director effectiveness and "overboarding"

How many directorships is it reasonable for any one director to hold at a given time? Recently, I met a gentleman at a function who introduced himself with the line, "I am a professional director, I sit on ten boards". Ten boards seems a lot. Is ten reasonable?

If we think what a commitment to ten boards looks like, the following picture emerges. If you assume that each board has a monthly meeting (of one day), and that directors spend one hour in preparation for each hour in the meeting, then a pool of ten boards means 20 days' effort each month. That's without allowing for committee meetings, crises, or any time to understand the company or the market within which it operates. This last factor (understanding the company and its markets) is crucial if a director expects to contribute to strategic discussions or assess proposals in any meaningful way.

On this analysis, directors with ten concurrent appointments are seriously "overboarded". They cannot hope to be effective. Think about it. You'd have enough trouble getting through the reading, let alone have time thinking, learning and assessing options. So, how many concurrent board appointments is reasonable? Experts suggest that a reasonable upper limit is four boards. Chairmen, with their heavier workloads, should limit themselves to three or possibly even two boards. 

While such reductions are likely to be contentious in some quarters, some serious benefits are likely. These include a larger pool of directors; a more diverse set of contributions; higher levels of engagement; and, crucially, better decisions (less groupthink). Overall, directors would have more time to govern well. The only downside I can see is the reaction from the very directors who wish to protect their positions and status. But that's probably a fight worth having, don't you think?