Yes: lots of info and personal experience.

It's very much a function of how clear the air is.

In clear air, 25 miles for a 2"x5" glass aignal mirror, and 45 miles for a 3"x5" signal mirror are about nominal for naked eye visibility - I've done that several times. In reasonably (but not overly) smoggy air - half that.

Range is greater when signaling toward the sun, less with the sun at your back.

Here are videos I made of the mirror flashes from my 3"x5" glass mirror at ranges of 0.7, 11.1 and 43 miles: http://www.youtube.com/watch?v=GwCbgQGmID4

A post on some of my 22-mile testing, with links to videos of the testing I posted on YouTube, are here:
Signal Mirrors at 22 miles: glass, metal, plastic

More references:
US Navy Test: "Mirror Flash seen 45 Miles"
Doug Ritter's Consumer Alert: "Phony Glass SIgnal Mirrors"
WWII U.S. Government Signal Mirror training film


BTW: My avatar image is a photo taken through the aiming grid of a signal mirror - that bright spot isn't the sun itself, but the virtual image of the direction the reflected light is going, produced by the retroreflective beads on the aimer mesh.