Earlier quoted context omitted.
Exactly. With a permanent UBI in place you can throw all these studies out the window.
You can argue that the only way to perform a completely accurate UBI experiment would be to run it for at least 60-80 years for everyone. Social experiments are very hard to do and have many flaws, but it seems unreasonable to say that the information gained by doing such studies should be "thrown out the window".
Maybe the simple solution is that the researchers establish a dedicated million dollar bank account for a participant and automatically withdraw $1000 for the participant every month.