Then they find out their 40 descendants don't want to give back any money and are forced to work 900yrs cleaning toilets to pay off that reverse aging, only to end up dying of cancer, because they aren't immortal.
You might enjoy reading Transmetropolitan - it's a comic where one of the aspects of the future it is set in is that people who are revived are pretty much unwanted nuisances that usually end up with severe mental problems. They do get nice new bodies, though.
That's why you leave your kids peppercorns in your will
Aren't there trusts that can protect against this?
You're trusting the living to not overrule the dead. A trust is only as good as the system willing to enforce it.
Ah yes many such cases from history of human race, when monarch want to govern, but impatient son is willing to coup whole establishment, just to govern himself. In best case, parent will just get blinded Byzantian style.