As soon as you have bought them really. though the painted plants often die due to the paint. depending on the species of cyclamen they may come again year on year. the hederifolium types are fully hardy as is coum though tends to be more of a spring variety.

As SBG says the painted ericas are not likely to survive... think about the fact they have had colour sprayed on them and therefore the leaves can't breath. As to cyclamen, which species are you asking about?