For an otherwise healthy post-menopausal woman with early stage HR+ BC and persistent AI intolerance, is there an age cutoff above which you would consider avoiding adjuvant tamoxifen therapy?

There is no age cut-off based on chronological age. However, physiologic age and comorbid conditions are what I would use. For example, a 72 yo with diabetes, hypertension, and coronary artery disease is likely to die of her underlying conditions and not early stage breast cancer (Ording et al., PMID 24130755). Whereas an 80 yo, with good functional status and no comorbid conditions, may live an average of 16 more years. Hence, reducing the risk of distant recurrence with tamoxifen would be appropriate. (https://www.johnhancockinsurance.com/life-expectancy-calculator.html).