In my mind Creme Eggs always go on sale, rather quietly, just after Christmas. And then they’re around until Easter (except in stores like CostCutter where you’ll find them all year round, though they do begin to taste a bit gammy by the time Hallowe’en comes round…). I guess with Easter being so early this year they’re marketing them a lot more early on.
And Cadbury’s already tried to capitalise on the Creme Egg fascination with a festive Cadbury’s Christmas Pudding which was aimed at the same seasonal confectionary fans. It tasted like sack though, so didn’t catch on.