Well, in 1E, it was re-usable. This was, essentially, a form of enchantment: If X happens, then do Y. The thing is, if spell Y had Concentration, it could remain active as long as X was occurring. If Y didn't have a duration, it would trigger once, but each time the detection spell 'pinged', then it would trigger again. It was a really nifty thing, and one I enjoyed quite a lot. I'm really hoping it comes back at some point.
Anyone else have thoughts on this?
Edit: Removed thoughts on Combat Spells -- I missed that they fixed that with 4E.
