Could you please point us to where you found the article stating Ich can live without a host for 3 months? Here is what I base my quarantine practices on
http://atj.net.au/marineaquaria/marineich.html
I like this site because it cites SCIENTIFIC studies from multiple sources. I don't mean to be rude, but "I read somewhere..." just doesn't cut it. Without backup in the form of sources/research, all it is is an opinion. I googled Marine Ich and couldn't find a single site agreeing with your 3 month hypothesis.