Since I couldn't really answer the poll in the post-FIRE thread, but am still curious.
Obviously everyone is different (reason for the personal in personal finance).
But, per person, what is your goal to have for income? Do you really plan to spend as much as you can of that, or is it more to make sure all bases are covered? (like LTC, health issues, ability to do more than you thought, etc)
If you are planning to be supporting someone else for at least five years (parents, children, whatever), include them in the per person amount.
I bring up "full retirement", rather than "barista fire", etc, so that at least one thing is level for the poll. So, assume even if you believe you'll work a part-time job forever, you cannot. You're aiming for your savings, investments, pensions, whatever, to cover you.