Director tenure is a topic of great interest in the corporate governance debate. Researchers try to assess the effects of tenure on director contribution, board effectiveness and firm performance. Regulators, corporations, and institutional investors advocate for term limits for outside directors to reduce the risks of impaired governance. Despite the burgeoning interest, there is lack of consensus on the mechanisms shaping directors' contributions over time. We argue that next to the ‘loss of independence’ and ‘knowledge acquisition’ hypotheses, respectively predicting a negative and positive effect of tenure on task performance, socio-cognitive and behavioral approaches elucidate the way in which directors' contributions rise and decline with time. Using a multiple case study approach, we document wide variability in directors' contributions at similar levels of tenure. We find this is due to a series of contingencies including whether directors are novice or experienced, the frequency and nature of board interactions, and the relative power of a director. This variability is particularly clear in longer serving directors for whom we find polarizing results: while some grow stale in the saddle, others sustain high levels of contribution despite extreme tenures. The latter finding is at odds with agency-based assumptions and general predictions from the literature. Overall, our study offers a tentative explanation as to why setting an ‘ideal’ tenure for outside directors has proven so difficult and encourages boards and policy makers to consider the influence of director-level features as well as board dynamics in shaping directors' contributions.

董事任期是公司治理辩论中一个非常有趣的话题。研究人员试图评估任期对董事贡献、董事会效率和公司绩效的影响。监管机构、公司和机构投资者提倡对外部董事的任期进行限制，以降低治理受损的风险。尽管兴趣日益浓厚，但对于随着时间的推移塑造董事贡献的机制仍缺乏共识。我们认为，除了“独立性丧失”和“知识获取”假设分别预测任期对任务绩效的消极和积极影响外，社会认知和行为方法还阐明了董事贡献随时间上升和下降的方式. 使用多案例研究方法，我们记录了董事的广泛差异 类似任期水平的贡献。我们发现这是由于一系列偶然因素造成的，包括董事是新手还是经验丰富、董事会互动的频率和性质，以及董事的相对权力。这种可变性在任职时间较长的董事中尤为明显，我们发现他们的结果两极分化：虽然有些人在马鞍上变得陈旧，但其他人尽管任期很长，但仍能保持高水平的贡献。后一个发现与基于机构的假设和文献中的一般预测不一致。总的来说，我们的研究对为什么为外部董事设定“理想”任期如此困难提供了一个初步解释，并鼓励董事会和政策制定者考虑董事级别特征的影响以及董事会动态在塑造董事贡献方面的影响。