It's common for coreopsis to die out after several years in the garden. It's not a particularly long-lived perennial. Five years is a good run for most coreopsis. Unless you saw evidence of disease, you can plant new ones in the same location with little danger of them dying out immediately. Large-flowered types such as 'Early Sunrise' often fade away faster than small-flowered threadleaf types (Coreopsis verticillata). 'Moonbeam' and 'Zagreb' are long-lasting threadleaf types.