I'm just hopping in here, to add my 2 cents. All my dends. are in plastic pots, with the exception of Dend. kingianum which are in terracotta. They do well in plastic pots, keep the dends. snug, they are much happier. But remember, plastic heats up when the weather does, so remember to water the dends. when they look like they are shrivelling. Don't fret so much about your orchids. Now you are in the winter season over there, you must still give some water to them, maybe on a fortnightly basis. You have got to think about orchids in the wild, growing on trees, they still get moisture from rain, dew, etc.. You could put pebbles in the base of the pots, would help drainage and keep the pot stable. Best of luck.