Slugs and how long will I be battling them

I tried to put a picture of a
slug here. Blech. Can't do it.

Last night I had to go out to the greenhouse at about 11. I had forgot to close up the greenhouse for the night. Yes, I spoil my tomatoes rotten. So I grabbed the flashlight. Slugs really creep me out, and I don't want to step on any. I went into the greenhouse to close the louvres and as I was leaving I pointed the flashlight at the basil bed. I was just asking for it, wasn't I? There must have been two dozen small slugs and two medium sized ones, all on the march to my precious basil. I grabbed my container of diatomaceous earth and started sprinkling. Thats right, right on them. By the time I was done I felt terrible. I went in the house and thought about how miserable they looked all dusty. This morning I entered the greenhouse unsure of what I would see. I saw nothing. There wasn't a single little slug body where I expected carnage. I was relieved, but I am wondering if there is a delay in the...um...passing of the slugs or does it not really work as they say it does. Anyone out there know the answer?