Interesting responses so far. Tax management seems to be complicated and depends somewhat on government future policy.
In the early years we deferred SS for me and converted IRA to Roth. Now with full SS and before RMD's, we are spending some from IRA and the rest from Roth to get to a moderate tax rate. I would credite i-orp with the idea of spending from Roth's rather then always trying to protect that money. When RMD's hit us, taxes will go up but we have enough Roth to keep this under control, unless the portfolio zooms up and IRA's with it ... in which case the extra taxes will be a minor annoyance.