How long do daffodils live in vase?

I sell bouquets of daffodils at the local farmer's market, and my customers have been telling me that my own experience is spot on. A cut daffodil should live a good week in a vase. A lot depends on its age when the flower was cut, but I've never done any of the complicated things people do to make bouquets last longer. Just give them fresh water, and be grateful for this sunny herald of spring.