Subject: Re: Reading tea leaves
one could wait until the 10th year and then take it all.
Nope.

Man, talk about going down a rabbit hole!

Google is your friend.
Required Minimum Distributions for IRA Beneficiaries
https://www.irs.gov/retirement...

Says:
Take entire balance by end of 5th year following year of death, {does not apply for most people}
or
Distribute based on Table I
* Use beneficiary’s age at year-end following year of owner’s death.
* Reduce beginning life expectancy by 1 for each subsequent year.
{ Note that this is different from your own IRA. Your own IRA uses the L.E. of your actual age each year. Inherited IRA starts with your L.E. of your age when the owner died, and subtracts 1 for each subsequent year, regardless of your L.E. at that age. It is not allowed to lookup or 'recalculate' a new starting life expectancy after distributions have begun.}

Leads to: https://www.irs.gov/publicatio...
Table I
(Single Life Expectancy)
(For Use by Beneficiaries)

This table starts at Age 0 with Life Expectancy 84.6.
Ends at age 120+ with LE 1.0

The entire table all by itself: https://www.fidelity.com/build...

whew!!!