This is an adjustable concept depending upon your asset protection comfort level. In the early 1990s, it was rumored that the Rockefellers had over 7000 of these trusts. And who knows how many sub-trusts they had under those . . . and sub-sub-trusts, etc.
The point is, "never put all your eggs in one basket". The more your assets are spread around in different entities, the greater the protection. But each individual has to decide for himself or herself, how safe or how dangerous one's life is, what level of divine protection one's estate may have, and therefore how many potential enemies or thieves one's estate may be facing . . . or not facing. If the threat is low, then less trusts are needed. It's that simple.