It only took one application to banish the annual powdery mildew infestation from my mini african violets. Very pleased.I would appreciate more information on when each packet was made or will expire, but since they are sealed in single-use packets, at least oxidation is not too much of an issue.Spraying african violets that are vulnerable to water damage is tricky. I recommend very warm but not scalding water, like baby-milk warm, and apply in a warm (80F) and humid room like the shower. After spraying, remove droplets with paper towel quickly before they chill the plant.The plant should smell of peanut or seasame, then the smell breaks down into the mildly stinky sulfurous compounds that fungi hate. If there isn't any smell at all, you were sold fake or old neem oil. It isn't really noticable unless you are within a 1ft or so of my plants, and it faded by about a week or so.The squirt bottle is plastic but decent. It has not leaked yet.I also like that Amazon sells refills. The small packets are a really smart idea. I only needed to use one packet for my small plant collection, and I don't have to worry about the rest of the packets. Neem oil loses its effectiveness within ~8-24hrs once opened and mixed!