How much longer do you think is needed?? Twenty-four hours is plenty sufficient to rule out any chemical processes.
Rossi only has an Italian patent. Other patent bureaucracies (including US) refuse to consider "cold fusion" as legitimate technology, putting it in the same category as "perpetual motion". One of the purposes of this demo is apparently to force the issue and get those bureaucrats to get on a stick.
You've got a point. David Copperfield made the Statue of Liberty disappear in less than an hour.