Airport Extreme assigning new IP addresses to clients

I run into the issue of not being able to get the same ip address assigned to a device in my home network. This is usually not an issue but since I have a media server set up with several players around the house which are controlled via browser and their ip addresses it becomes an annoying issue. I have gone and assigned static ip for some of those nodes but I am wondering why airport extreme does not renew the same ip to the same mac address in case the device gets off the net and comes back on?
I never had this issue with any other router I used...it seems logical to assign the same ip address to the same mac address. Is there a configuration issue with my airport extreme...I went and changed the lease rate to 365 days and still have the same issue.
I appreciate it if someone familiar with this problem could chime in.

Cheers,
Matt

Been the same on any routers I've used at home, haven't been that many over the years; SMC, Linksys, D-Link, TC.

Am no network guy and never checked into why. Can only assume the IPs are released whenever a device shuts down, goes to sleep, etc. and the router assigns IPs in numerical order as they come back online.

My experience with all the other routers through out the years has been different. when the client goes offline and comes back online and if its previously assigned ip address is taken I could understand but the router assigns a brand new address even though its original ip is available.
It just doesn't make sense if you have port forwarding set up as many do for file sharing and media sharing if you have to continuously change those configurations. More importantly, if the change occurs while you are remote and need access to a file you will be stranded.

So I was able to get around the issue by reserving a particular ip for devices that must be configured with same ip address...there seems to be problem when other machines come online and airport tries to assign them an ip address. I have noticed that my media server goes down for no apparent reason and I have to reboot it and start the sharing process again. Also, some machine try to get the reserved ip address and won't come online unless ip is released and reassigned a new ip address. Is there a solution for this or I have to live with these problems? I appreciate any insight anyone can provide.
Cheers,

Assuming that your AE takes it's DSL connection from a router/modem - use DHCP assignment from that, instead of the Extreme - i.e. use the AE in Bridge mode (defined under 'Internet Connection' in Airport utility). It sounds to me like both the router and AE are distributing ip addresses, causing the ip hopping following 'sleep'.

Let me know how you get on

the dsl modem is configured as a bridge and the ae is connected with pppoe to the isp otherwise there is no use for the ae. The idea is to use ae as the local network and have it assign the ip addresses.
Before hooking up the ae I had the dsl modem to connect to the internet and create the home network never had any issue with dhcp assigning the same ip to the same mac when it was available.

Finally found something on the net that described the problem with dhcp ip reservation...it's just too funny and I remember the episode in seinfeld vividly! Gotta give the work around a try!
http://arstechnica.com/apple/news/2007/03/airport-extreme-does-seinfeldian-dhcp-reservations.ars