It was done in Russian with dogs in the mid-century and done again with monkeys in Cleveland at the end of the 20th century.
Complications in the USSR were because of infection (animals lived for upwards of a week and were not on artificial organ machines).
I don’t know enough about the Cleveland experiments to know how long they lived.
The x files movie I want to believe. One of the best for Mulder and Scully.
Maybe the technology has advanced to the 99% probability of survival stage.
He has nothing to lose....................
A little over a week; I had the pleasure of working at Case Western (where the experiments were done) with of one of the scientists who participated. He had good stories. He felt they went too far, and lots of regrets about their work (and nightmares about the monkeys), but I don't believe Dr. White (the actual project lead, and a true genius and wonderful man) had any regrets, save they weren't able to take it further.