Does limiting mental activity during the day increase mental performance later in the day?
Very interesting question, however, cognitive exhaustion may be a learned phenomena ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5413468/ ) as referenced by this 2017 article finding it to be conditioned to the individual. Though I cannot provide a concrete answer, I would estimate that cognitive stamina, so to speak, can be trained into the individual much like aerobic or muscular stamina.