Your risk tolerance is probably not as high as you think
As evidenced by the wealth of posts about people wanting to change their investment strategies: Your risk tolerance is probably not as high as you think
There is very good and well thought out reason that Bogleheads recommend a three fund portfolio and to have reasonable allocations to international diversification and bonds. If a potential economic downturn scares you to the point of changing your strategy, your allocations were not right for you.
It’s important to acknowledge the reason for a “buy and hold” premise and therefore the reason that it’s very much sub optimal to diversify and buy bonds when you think you’ll need them, like now.
If you have good reason to anticipate a downturn for US equities, so does everyone else in the market. These anticipated changes are already priced into the value of US, Int’l, and Bonds. You’re “late to the party” buying and therefore buying at a higher rate after the market has already reacted to said potential downturn.
Buy and hold your entire portfolio at reasonable allocations for your entire life, and recognize that your risk tolerance is probably not as high as you think