I think one might consider putting, say, 1.5% of one's portfolio into short positions, preferably with asymmetrical payoffs using options.

e.g., you could probably pick a little basket of things which give you (say) 2/3 chance of losing it all, and 1/3 chance of making 5 or 10 times your money. A one-time boost to your portfolio of 10% is nothing to sneeze at. You could ease into it over time.

The salient question is when to start opening those positions. Not yet, is my guess. It's extremely rare for the market to drop materially (and in a lasting way) within a short period after fresh recent highs. (and the most recent one was only 3 trading days ago). If there has been a recent high the speculative juices are still flowing, meaning most traders active in the market people are still very FOMO. Hesitant to give up, and quick to buy on a dip. I find that wears off after a while.

So...maybe the time to buy insurance is when it has been at least a little while since a fresh recent high.

Jim