I think all petunias are perennial, it is just that we of the 'neat garden generation' don't like the 'leggy half dead' look. So we treat them as annuals and out they come for something new. I have had petunias that lived for years but they do go through a stage off messiness in their off season. Always seem to flower well though.

Thanks Kolanda. I have a lot to learn. I think I might create a kind of nursery or hospital area up the back corner of my backyard where I shift things, prune them, wait for them to come back, then plant out again. Might save some bills and adds to the satisfaction. Also gives the opportunity to have stuff on show before the nurseries. Chrysanthemums are another flower I have in a pot that seem to be on the way back after a big haircut.