... While we are enjoying giddy prices every day, it seems, I do miss the buying opportunities at lower prices. "Lower" is a relative term, no? We have been spoiled by cheap opportunities (most recently 2015); Rear view mirror for sure.
The eternal Berkshire investing dilemma & paradox!, longinvestor. -Next time the big US banks lie crushed in a big pile, - and that will happen again - Berkshire is likely to become cheap [relatively] again. Good to have at least some cash ready for that. It's personal, how much, though. Some less, some more.
On the other hand, if one doesn't actually own BRK anywhere near what one actually want to own, just start buying, and time combined with Berkshire will do one good.