I heard that dishes that stood for over one year, even if they were treif, even if they are made of porcelain or ceramic are OK to use, even for Pesach (after Tvila). Is that true?

There is an opinion that china dishes after they have stood for a year may be used. By extension, some people are lenient regarding porcelain and ceramic although this is not stated in the Halacha. Make sure that you do Hagala three times.