How can I keep carnartions longer?

My favorite flower is pink carnations and this valentine's day got a bouquet of em from my finacee and I want keep em alive for longer than just a week.

How can I keep carnartions longer?
this has always worked for me:

Every other day empty the water, wash and rinse the vase.

Rinse the ends of the stems with tepid water (not soft water though) cut the stems at an angle under the running water.

Put fresh water in vase, put a 1/2 packet of flower fresh and mix well, put the flowers back in the vase.

If you have no flower fresh use about a 1/2 cup of sprite, 7up, or ginger ale.

Your flowers should last almost 2 weeks.

In another posting I reminded everyone.

Remember that these flowers were actually dead when you got them (cut from their roots) so getting a week of enjoyment out of them is great.

Enjoy your flowers!
Reply:use an asprin
Reply:I've heard a bit of 7up or Sprite (obey your thist ... Kobe told me that) will help them stay nice longer.
Reply:A penny in the water works. An aspirin in the water works, too. (Based on my own experience, I'd say it works a little better.)
Reply:Carnations are long lasting flowers, will last more than two weeks. As long as you make sure there is enough water for these flowers to drink, they'll be happy. The other poster is very correct in his suggestion of changing water every 2-4 days, and clipping off the stems at an angle with sharp knife or scissors before setting them back into the clean vase with fresh water. My customers say they enjoy their vase of carnations for a long time.