I wouldn't say a strict ordering would even make sense for most people. For tax purposes it's generally optimal to keep your income as consistent as possible from year to year. Achieving this in retirement would generally require taking a bit from Roth, traditional, and taxable each year and sticking with that plan. Certain things (Obamacare subsidies, social security, pensions, RMDs from retirement accounts) might make it so that in your situation it's better to do one ratio of withdrawals for a certain period of retirement and then switching to a different ratio when a particular event happens.