maybe it would be a Good Thing™ to take that entire 2024 gain and put it into T-bills. It sure would be nice to protect that gain.

This sounds very much in tune with my thinking.
But...
the catch is that it would have sounded sensible in at least half the last 20 years. It could be a long painful wait!

I have written high-strike calls against essentially all my long Berkshire position, leaving me relatively neutral. But I'm stroking my chin, considering actually selling some of the long-term longs, which would leave me somewhat net short. Just considering, mind you.

I pencilled in the most plausible return from the longs in the next 6/12/18/24 months and it's not pretty. If the stock is trading at (say) 1.4 or 1.45 times book in the next year or two, how fast does book have to grow for today's price to look attractive, and is that growth rate at all plausible?

For example, imagine the following scenario. Adjust to suit your tastes.

Book per share remains about as good a metric of value as ever, for another few years at least.
Book per share grows 2.5% per quarter in nominal terms (10.38%/year)
Monetary inflation rises 0.8% per quarter (3.24%/year). So, real book per share rises at 7.14%/year. (growth since end 1998 has been infl+7.23%/year)
Typical valuation multiple by price/peakbook in the next few years is just a bit above the 1.397 average of the last 20 years, let's say 1.42.
From today's price of 456.35 per B, that's a two year return of inflation + 1.9%/year. Three years of inflation + 3.5%/year.

When one remembers that valuation levels spend about half the time below the long run average, occasionally far below, the various short to medium term prospects are not particularly compelling.

Jim