By neem I mean real cold pressed Neem, not that extract crap, to spray on their trees to prevent bugs and such? Any idea on if it will work on leaf miners?

I use it. Other than the smell, its pretty good for mites and scale. Leaf miners I have really no experience with because of where I live.

It works for CLM, the duration of its effect being dependent on the weather conditions.

I use it on my container trees against aphids. I put one small spoon in one liter of water and spray the leaves. I started this treatment 2 weeks ago, so it is still too early to predict.

I was reading a couple books on organic gardening and figured it couldn't hurt to get my trees on a two week spray cycle until the weather gets too hot to do it of Neem and then continue with pure liquid fish(not the extract) and see how things are going. Its still early in the season.