In 2016, a large, multi-lab (k = 23, N = 2141) replication trial was undertaken. It failed to demonstrate any effect of ego depletion (Hagger et al., 2016). Baumeister, the originator of the concept of ego depletion, objected to the results, arguing that the task used was not suited to demonstrating ego depletion (Baumeister & Vohs, 2016). His objections seem to be valid. Baumeister announced that he would conduct another large-scale replication trial, with a test protocol that more closely matched those used in ordinary studies of ego depletion, but (to my knowledge) he has not yet done so, though others have undertaken this task.
A large (k=12, N = 1775) study published in 2021 successfully replicated a study showing an effect from ego depletion (Dang et al., 2021).
Another large (k=36, N = 3531) study found no ego depletion effect with the pre-registered analyses (Vohs et al., 2021). Baumeister and Tice (2022) wrote an opinion article arguing that this study failed to show an effect because it excluded a third of its participants (from Vohs: "Based on preregistered criteria, we excluded 30.25% (n = 1068) of all participants in confirmatory data analyses, most often because of excessive errors on the E-task, not being a native speaker of the laboratory’s language, or failing to comply with instructions to not use their phone."), and that when those participants were included, the study showed a strong ego depletion effect.
Baumeister et al. (2024) summarized the current status of ego depletion research:
Ego depletion theory proposes that self-regulation depends on a limited energy resource (willpower). The simple initial theory has been refined to emphasize conservation rather than resource exhaustion, extended to encompass decision making, planning, and initiative, and linked to physical bodily energy (glucose). Recent challenges offered alternative explanations (which have largely failed) and questioned replicability (which has now been well established). Methods have improved, particularly with emphasis on longer, stronger manipulations to ensure fatigue. New work extends ego depletion into workplace settings and sports. Interpersonal conflict may be both a major cause and consequence. New questions include the possibility of chronic ego depletion (e.g., in burnout), protective factors and coping strategies, individual differences, and recovery processes.
Ahrens suggests that ego depletion can be reduced, in the context of knowledge work, by using a note-taking system (Luhmann's zettelkasten, in this case) that prescribes how notes should be taken, which is the same in every case (Ahrens, 2017, 9.6).
A 2011 study comparing younger participants (<25 years) to older (40-65 years) found that the younger group showed ego depletion effects, but the older did not (Dahm et al., 2011).