@Taxes-by-Rocky  You hit two nails on the head:

there is one variable that is almost guaranteed: once you pay that tax on the conversion (or salary), you won't ever be getting it back.

medical costs and nursing home costs have a funny way of approximating those RMDs, potentially reducing or eliminating their tax bite altogether

@qbteachmt And another point well-hammered

Paying tax on conversion or paying tax on distribution is the same,

But I don't understand the rest of your observation:

and there isn't as much time for tax free growth

Regardless of the time period, the end result is going to be the same, assuming rates don't change. $100,000 compounded at 5% for x years, times tax rate at distribution, is going to be the same as ($100,000 minus taxes) compounded at 5% for x years.

Which brings up the point that no one here mentions:  All the crazy Californians who are doing their Roth conversions before moving to Nevada or Texas, and all the crazy New Yorkers who are doing their Roth conversions before moving to Florida.  If we're going to be blind people describing the beast, at least tell us where the elephant is located, and where it might be headed.