Hi U2SockMonkey,
I tried your suggestion, "After you get connected and you're playing music over AirPlay on your 4S, take a walk down the street and move out of range if your wifi network. Once you've done that, return and try playing music on your AirPlay device again. This typically will allow playback for 10 - 30 seconds and then it crashes again."
When my iPhone 4s is airplay streaming to the isolated, non-networked, Airport Express it works flawlessly I can leave the house, return and start streaming immediately and indefinitely. Since it is not connected to a network, there is no network to crash.
On the otherhand, when I use the same iPhone 4s to access the other Airport Express (identical BTW) that is part of my home network, it crashes in 5 seconds and takes down my Qwest router and network. Every time.
I still have my iPhone 3s. It is using iOS 5.0.1. It can airplay stream to either AX, the stand-alone one or the networked one. No problem. Plays indefinitely.
My partner has iPhone 4. It is using iOS 5.0.1. It can airplay stream to either AX, the stand-alone one or the networked one. No problem. Plays indefinitely.
The only combination that is a compete and utter FAIL every single time is iPhone 4s and a NETWORKED Airport Express.
So, if you want to use airplay on iPhone 4s while waiting for Apple to do a software fix, you'll need to separate the Airport Express from the home network and not use it as a "bridge" or "extender" and absolutely don't let it "join" the home network. Instead, use the AX out of the box (or restore factory settings) plug the mini-stereo cable into the jack before plugging the AX into the wall. It will, by default, create its own weird stand-alone apple network. You'll need to switch to and join that separate network on the iPhone 4s. Then you can airplay stream to that AX indefinitely. If you want to stop the amber blinking light on the AX, you'll need to go into Airport Utility and configure the separate AX. The AX is blinking because it is unhappy not having an internet connection (among other things). You can configure it to "ignore" those issues, and it will turn solid green. You can also rename the apple network there, and name the speakers. I call the network and the speakers with the same name (dining room speakers). You can also add security (password) if you are so inclined. But the worst that happens is a neighbor might stream music to your speakers. There's no internet, so there's nothing to connect to or snoop on.
That is another point. When your iPhone 4s is signed on to this new stand-alone AX netowrk, you will not be able to access the internet. So while you are Airplay streaming, your phone is crippled. It keeps trying to use the AX network to obtain data, but the little AX isn't sending any.
BTW, using an AX in this non-networked mode is fantastically more robust than when it is networked. I have had zero music drop-outs airplay streaming to it, or using iTunes to it. On the other hand, my other networked AX still drops the music every once in awhile. Go figure.
I'm not endorsing this as a "solution" to the problem. It's bizarre that my iPhone 4s won't play nice with a networked airplay speaker. But it is something that might work for those of you who do not need your airplay speakers connected to a home network.