The 5 years they are going for just doesn't seem long enough for the reason that if you actually choose not to work during that time, you will very likely be completely screwed at the end of the study when you need to get a job again (similar to mothers leaving the work force for multiple years to raise kids). A person evaluating their options in this program is thus much more likely to use the UBI as supplemental income than as a job replacement like they might if it was guaranteed to retirement age. This is still great, but I don't think the results will be overly indicative of outcomes in a nation-wide rollout scenario.