That four hour time can be more than is needed. It's for dirty, cold water.

http://www.katadyn.com/usen/technical-support/micropur-support/

Of course, it doesn't say whether clean, warm water should have the 30 minute or 4 hour treatment time to treat cysts....

The wait time is why thru hikers often get the Aqua Mira Frontier Pro - which is NOT suitable to rely on it for anything but filtering the largest critters out - but, cysts are quite large by comparison to bacteria. So a pass through the Frontier Pro followed by 30 minutes with chlorine dioxide does the trick.