Additionally, I'd recommend se percentage be invested in the Vanguard total bond market fund as well. Holding se percentage there will reduce overall portfolio volatility, and can actually increase returns slightly.
In order to maximize return over your preferred time frame (while minimizing risk), you have to examine the whole universe of investable assets, examine their volatility as well as correlations amongst themselves.
From there, your goal is to assemble an ideal basket of assets maximizes your return for your personal level of risk. Running these filters and choosing when to rerun/rebalance is the basis of modern portfolio theory.
Managing your money using MPT is the service that many investment houses sell. Rolling your own is absolutely possible, but it is not as simple as stocks vs bonds.
Having run a lot of simulations in determining my own portfolio I came to the conclusion that these things affected my returns, in decreasing order:
1. annual maintenance costs 2. tax effects 3. choice of index 4. diversifying beyond stocks/bonds
I imagine most people who aren't using a passive strategy can chop 1 - 1.5% off their costs just by switching to indexes, and the remaining optimizations will pale in comparison. But as the size of the portfolio increases the additional effort becomes worthwhile.
It's possible that over the long term the market will decouple again but keep in mind that most investment advice about "universal truths" about the "long term" are based on a little over 100 years of market data. Given that I started investing at age 20 and will hopefully live to old age, that's not a lot of training data in comparison to the amount of prediction it's generating.
Unrelatedly, what are you thoughts on the permanent portfolio (if you've heard of it).
25% in physical PMs is hard to justify but generally speaking I think Browne's Permanent Portfolio is a good base. Perhaps 20% each of domestic equities, international equities, PMs, cash and long term bonds would be more realistic, with rebalance bands at 17/23.
1: https://investor.vanguard.com/mutual-funds/target-retirement...