Oh! That's a different kettle of fish entirely; I'd tend to say yes, even without needing to reduce the power of the item, though again it would depend on the effect. For example, if you can get the power high enough, I'd let you make a potion that replicates the reiki healing spell, and applies the effect in a single action rather than requiring many minutes at a minimum. (Of course, that's because you already spent *hours* preparing the potion... details, details.)
On the other hand, if you've got a massive 20 slot enchanted item specified as a magical portal generator that flings you through the nevernever to anywhere in the world... that might take some time to get the thing aimed in the right direction, powered up, and ready to go.