The recent threads here about selling BRK (or APPL or anything else) based on market price and its relationship to book .................... seem very un-WEB-like and un-Charlie-like to me, and they surprise me a little. Math is important, but it isn't everything.

I have held BRK for almost 30 years, through runups and LONG periods where the stock hardly seemed to move. When it fell (rarely), I bought more.

That's easy to do if you are in the 1st half of your life, with constant income streams coming in from your work, and saving/investing part of that.

My impression is that nearly all posters here are not in that situation any more, are (partly far) into the 2nd half and adapting to that changed situation. Without constant income from work and - as many have written here - a Berkshire paying no dividend being their by far largest or - in my case currently - even their only investment: Where should that money to buy more if it falls come from?

In such a situation it's naturally the other way around, that you have to sell some shares of your largest/only investment from time to time to finance your living --- and for that Math is everything.