"... by the time it gets down to the great-grandchildren, someone, somewhere along the line, will have managed to piss it away... "
I used to work for a perfect example of this. The current owner's grandfather founded the business with two like-minded friends and did moderately well, acquiring a reputation for high quality work in the process.
The next generation bought out their partners and built up the firm and workforce with careful investments in the quality, production and relevance of their products. They deservedly made a substantial amount of money in the process.
The current owner seems to be swayed by the "fad of the moment" and has invested in vanity projects, advisers and his lifestyle. The firm now has a new, bespoke HQ, has outsourced most production overseas, and the quality of its products has dropped noticeably. The factory site was recently sold off for housing.
His children think they are going to inherit a money mine and behave accordingly.