If you have encountered a harvest getting destroyed in a very short time before, I think you have a valid reason to use it preemptively. I don’t know too much about Neem oil actually but I know that in India they ingest it directly as a traditional medicine and that type of use has led to seizures and hormonal problems. I’m unsure how much of those effects transfer to use as pesticide on produce but I still wouldn’t spray lettuce with Neem oil that I’m planning to eat the next day. I would at least research its safety further before deciding.

Have you thought about netting? It’s very ugly but it’s quite effective, as long as you apply the netting before the pests have arrived on the plant. It’s one of those tricks that a small scale grower can use but large scale growers can’t.