@Arthur,
I have the main Bell Aliant FiberOp router made by Motorolla. It acted as the main dhcp network for my home network and wireless throughout the house. From there, I have an airport extreme that was connected to this router as connect to an existing network. Extending didn't work. I also have 4 airport express around the house where I connect $99 Bosse speakers so I can listen to my music through airplay. Also, I have 2 apple TV, Mac pro laptop, iPhone and iPad2.
All of my airport express were cutting out at different times independantly. Very frustrating, annoying and embarrassing when company is home. So from there, I didn't know if it was my network topology creating this issue so I decided to isolate out the Airport extreme. I made the Aliant router the dhcp (which it was all along) and attached all airport express wirelessly to that router with static IP address. The results were 98% good with no cutouts except for once in every 2 weeks of so. Not sure why, really. A router reboot solved that.
Then I decided to change over to the Airport extreme. I removed the dhcp and wireless from the aliant router, rendering it as a simple fiber router with no special function. I setup the extreme with the internet static IP to connect to the Aliant router by giga ethernet wire. Then I wirelessly connect everything in the house to the extreme both wired and wireless. Awfull results. Cutouts were every few minutes and very discouraging.
So there you are. I really am a fan of airplay but now I am positive, by isolation, the extreme is causing this failure. Is it because I have too many devices connected? I tried splitting the wireless by creating the 5GHz network and connecting the 4 express by extending the network. It seems a little better but still cuts out every 10 minutes or so. While one cuts out, I can hear the other one still playing. So I know it's not the source itunes playing the music cutting out.
So I'm going back to my Aliant router, removing the extreme out of the mix, and connecting all express to the Aliant router by "connect to a network"' I would prefer extending but that only works on the extreme (unfortunately). So I have to decide between music that don't cut out and extending the network. The extreme loses. I want my music uninterrupted by crappy cutouts. My Aliant router works whereas the extreme craps out.