Loosing IP address after sleep

Question

I've read several threads on similar connectivity issues, but haven't found quite the same situation, nor a solution that works for me. So here it is, I hope someone out there knows what's going on and will be able to help out :-)
Problem: Wireless devices in my house tend to not being able to rejoin my home wifi network, either after waking up from sleep (laptop, ipad, AppleTV), or when getting back into range (iPhone when I get back home).
Affected devices can see and join the Wifi network, but don't always get an IP address. iPhones switch over to 3G/4G. (spinning wheel instead of a checkmark next to the Wifi network name in Settings > Wifi)
Fix (temporary, hence this post): reboot my Airport Extreme. This makes all wifi devices connected and happy again... until next time
Other interesting facts:
- This is not systematical (thank God!). Most of the time, laptops and phones automatically rejoin the network, but the frequency of incidents is clearly increasing in the past few years, now almost every day.
- I replaced my Airport Extreme some time ago, while still under warranty, but the issue reappeared soon after, with the new base station. Not a hardware problem!
- to reboot the Airport Express, I almost always have to unplug it for a few seconds because it tends to ignore Aiport Utility's "restart base station" command.
- My main computer, which never goes to sleep, never loses its Internet connection. When I try to "test it" and put it to sleep, then waking it up, it gets right back online all by itself.
- All firmwares are up to date, according to Airport Utility and Apple Software Updates.
Config:
     8-year old ADSL modem, running PPP (Provider: AT&T)
     AirPort Extreme connected to modem, WPA2 security, DHCP, USB Printer sharing
     AirPort Xpress, in "network extension" / bridge mode
     Clients: various Apple gizmos,
Has anybody else encounter this problem and found a more "permanent" fix?
I can provide more DSL and Airport setup details upon request :-)
Thanks in advance for any help or pointers you may have,
HK

Answer 1

I use to have that issue as well. I upgraded router when I started dual boot with Vista, then I had trouble last year with Windows 7 and problem is now gone, totally, never to return. Thanks to new modem.
You might get by with firmware updates to modem/router/switch, but for me, biting the bullet and not having to deal with lost connection was worth it.