Flowers are the best gifts ever!!
Nobody can disagree with this. But, when it comes to gifting flowers, some think that they wither away in 1 or 2 days. This is not true. Here is a small list of flowers that last long and remain fresh for atleast 10 days, provided proper care is taken, viz., maintaining 1) Fresh water every day and 2) cutting (slantly or obliquely) the flower stems at the bottom every day to enable the flower to take water.
Even roses can last and remain fresh for about 5 - 7 days, provided the above care steps are implemented. But, if you really are looking for flowers which remain fresh for more days, here is a small list:

Carnations - The meanings of carnations include fascination, distinction, and love. Like many other flowers, different messages can also be expressed with the flowerâ??s different color varieties. Light red carnations, for example, are often used to convey admiration, whereas the dark red version expresses deeper sentiments of love and affection. White carnations are associated with purity and luck, and pink carnations are often given as a sign of gratitude. In the early part of the 20th century, carnations became the official flower of Mother's Day.

Lilies - The Chinese and the Greeks had linked white lily to purity. To the Chinese, the symbolic meaning of lily is summer and abundance.

Gerbera Daisies - Gerberas signify innocence and purity, and daisies are also a classic symbol of beauty. However, the gerbera variety holds an added meaning of cheerfulness, which stems from the assortment of colors available. An assorted bouquet of gerbera daisies can lift the spirit and sending one is an ideal way to brighten someoneâ??s day.

Orchids - Orchids are a long-lasting and particularly elegant type of flower, making them the perfect gift for many occasions. Their graceful appearance draws immediate attention, and their reputation as an exotic and unusual flower evokes a sense of refinement and innocence.

Anthuriums - Anthuriums are one of the most popular tropicals with a long vase life of about six weeks and even more depending on the variety and season.

Birds of Paradise - The name Bird of Paradise comes from the spectacular flower shape, which resembles a birdâ??s beak and head plumage.

Alstroemeria - Alstroemerias signify wealth, prosperity, fortune.

Sunflowers - Bright and cheery, bold yet comfortable, the sunflower is a warm and caring gift. With brilliant yellow petals that surround the flower's center, sunflowers have an unmistakable sun-like appearance that has made them a passionate flower choice for many.

Chrysanthemums - While chrysanthemums generally denote cheerfulness and rest, individual colors do carry specific messages: red for love, good luck and best wishes; white for truth; and yellow for slighted love. Chrysanthemums will be welcomed throughout the British Isles and North America for any occasion. In Italy, however, their exclusive association with the dead makes chrysanthemums acceptable only for funerals.

I would be glad if somebody can post more flowers that last long.