Some flowers have a heavy texture and some a very light texture. Those that are heavy will last far longer than those that are thin and wispy. I try to put my stems into water. I cut out plastic mesh to fit over different bowls, and I just stick those stems through the mesh and into the water that fills the bowls. The mesh keeps the flowers from touching the water but allow the stems to stay in the water. I should file for a patent.
My wife says I am so smart it sometimes scares her. What a joke that is.