1. Fresh lavender will last up to ten days arranged in a container of water if you simply want them filling up the air with their fragrance and looking pretty. They will only last around 10 days. If I have extra lavender, this is what I do, especially in my kitchen where a lot of the family dynamics happen in my home. It helps relieve stress and calms the nerves, so that’s a must in a home of two boys, a moody teenage daughter, a German Shepherd pup, an asshole cat and a grouchy retired veteran for a husband.