Setting a proper time horizon is a crucial step in planning for retirement, and is typically done by making a reasonably conservative estimate of life expectancy... perhaps with a few extra years for padding, depending on a client's preferences.
Yet in many cases, planners adopt a uniform "standard" assumption for clients, without adapting it to even the most basic client circumstances, like whether the client is a single person or a married couple, despite the material difference between individual and joint life expectancies. Similarly, while the reality is that there's a high likelihood that a married couple will live several decades in retirement, the odds are overwhelming that for much of that time period, only one - but not both - of them will be alive.
As a result, it may be time for planners to begin to adopt more nuanced life expectancy assumptions for clients, at a minimum making a distinction between individuals and married couples, and with reductions in the later years for married couples to acknowledge the fact that while it's likely one may be alive, it's very unlikely that both will live through the entire time horizon. Otherwise, simply choosing an arbitrarily long time horizon for clients, paired with a high standard of Monte Carlo success, may actually result in an unnecessarily constrained retirement lifestyle!