Promed reports that:
a CDC expert surprised the others by revealing that the virus can remain potent on objects much longer than previously thought. "....in their studies, they found that you could still culture viable virus from surfaces after as much as 24 hours, which is longer than we normally expect viruses to be able to survive in the environment."
Susan Compton, also on Promed, comments:
I am unaware of any literature on the environmental stability of human coronaviruses, but rat coronavirus, which causes a pneumonia in rats, when dried on plastic and then rehydrated 48 hours later is still viable. The decrease in viral titer is 1000-fold after 24 hours and 10 000-fold after 48 hours (Laboratory Animal Science 43: 403-4).
This might go part way toward explaining the Metropole Hotel and Amoy Garden's outbreaks.