Angraecum didieri flower died after 1 week

[basicallyeileen]

Hello everyone. I bought an Angraecum didieri in bud, and waited patiently for it to bloom. It's a healthy looking plant, and the flower opened and smelled heavenly, but after a week, it faded and died. I've never had an Angraecum before. Is this normal for this plant? I had kept it on a south windowsill and watered it twice a week. I'd love to know if I did something wrong. It was such a beautiful flower, I wish it had lived longer. Eileen