From what I've read you have to be pulling water from a sewage-impacted puddle in a 3rd world country in order to get crypto in the quantities used for testing.

In the remote areas of the U.S. and Europe Cyrpto is pretty rare, so much shorter times have a very high chance of killing the one or two spores that are unlikely to even be in the water.

I have the Miox and feel comfortable with the 30 minutes called for Giardia.