Fellow Mustachians,
I've searched around the forums and elsewhere online as well as constructed a few spreadsheet to figure this out, but I’m still struggling to come to a conclusive answer. I am trying to figure out how to allocate my investments to optimize what I call the Double Shark Fin of Early Retirement. Obviously with the goal of moving the start of early retirement as soon as possible, while ensure the money will last until my wife and I die.
If you read the normal FIRE guidelines the advice is to save as much as you can, maximize tax sheltered accounts first, then pad after-tax account with what is left. But that advice is counter to our ability to live off of those savings in early retirement. In order to pull the “eff you! card” on your boss you’d need accessible savings in taxable accounts to live off of until you can access tax sheltered savings like 401k, TSP and IRAs (I understand there are tricks like the Roth IRA ladder, but let's keep this is simple and conservative for now).
That scenario might look like this:

Like most people who are aspiring to financial independence I’ve been saving 50-70% of my income. I started by putting everything I could into my 401k. As I got promoted at work and my income grew, I started to max those vehicles (both the 401k and a Roth IRA) so I dumped the excess into vanguard index funds.
My situation looks more like this:

You can see that as of today I have ~75% of my savings in tax sheltered accounts, and ~25% in my vanguard fund. Calculating our net worth, my wife and I have almost half of our goal (25x our annual spending rate) in our ‘stache. We are starting to see light at the end of the tunnel!
The question for the group is:
In these final couple years of savings, how to we determine where to put our money to optimize its value towards early retirement? If we retired today, we wouldn’t have enough money accessible to live off of until we could start drawing from our traditional retirement accounts. But if we shoveled more into our vanguard fund, we’d be missing the tax savings the 401k offers.
Thanks in advance for any help!