How many Airport Expresses possible?

Quoting from Apple's Airport Express FAQ:

Question: Can iTunes send a single AirTunes stream to multiple AirPort Express stations?
Answer: Yes. With iTunes 6.0.2 or later, you can send an AirTunes stream to multiple remote AirPort Express units, provided that each AirPort Express has the latest AirPort firmware (available here). The maximum number of remote AirPort Express units is three to six in typical conditions. The number that works for you will depend on your environmental conditions (such as building composition and local radio interference), distance to the remote AirPort Express units, and available network capacity relative to your other usage.

The practical limit on the number of Airport Express devices you can stream to at one time (as indicated in that paragraph) is determined by the available bandwidth of the wireless network.

The next question, of course, is how many could be supported if all Airport Expresses were cabled to an ethernet network.

The 3 to 6 stuff is wierd and trying to get a straight answer from anyone is difficult. I went to the Apple retail store and asked about this and then asked about how many could be supported if using ethernet cable. All I got was puzzled looks. In the configuration I was planning I might have as many as 7 AXs that are hardwired. Not a real clue if that will work and its sad no one has an answer.

Well... if 3 to 6 will work over a wireless connection, I suspect that 7 will work just fine on a fully cabled network.

It seems the only practical limit on the number of Airport Expresses you can stream to is limited by the available network bandwidth, so everyone's own experience may vary. That isn't so difficult to understand.