I grow many Echinacea because they're one of my favourite summer plants. I do not grow them in pots for fear of our UK winter cold/wet combo killing them off, as pots left outside do hold far more moisture than is good for a plant in winter. That said, if they are in pots they can easily be put under cover somewhere or an old wheel barrow put over them during the worst winter weather without harm.

Cut the flowers down after flowering and leave alone until the foliage eventually dies back, then clear away the debris. You should have just the dried flower stalks on the surface. Then you just have to be patient for April to arrive.

If you doubt their survival. Just tip the pot out and check the roots. White firm ones are healthy. Dark sludgey ones are not, remove. This quick check works with most plants and can save you a lot of wondering. . . Giving more time for you to obtain their replacement.