What are the options to shelter cash for the long term?
Looking forward, I am going to have a tax train wreck when I get to age 70.5 (currently I am 52). TSP, 401K, IRAs and my wife's SEP (she's 2 years younger than me) all come due for mandatory distributions. Due to some really good fortune, its likely we will never need this money to live on - my preference would be to "let it ride" and let my wife pass it on to the kids or wherever in her will.
My current employer doesn't allow after tax contributions to the 401K, so no mega Roth opportunity. Wife has an IRA and a SEP account, so no backdoor Roth for her. I do not have an IRA but do have the 401K and TSP accounts, so I could (I think) do a backdoor Roth for myself. We have a "whole life" insurance policy we contribute to, only because I can park after tax cash there to grow tax free (its technically insurance not an investment) but it gets crappy returns and has high fees.
What else is out there?