Wirelass access point issue

Hi, first a quick introduction. I am a firefighter, I have installed a wireless router in our fire station for internet access while not out on any calls. The main router works fine. The station is quite big so to spread wireless access around the station I carried out the following: Main router is the dhcp server issuing ip addresses from 192.168.1.50 to 200, the main routers ip is 192.168.1.254. I wired 2 additional routers to the first and placed them in parts of the station with no access. I turned dhcp on these 2 routers to relay to 192.168.1.254, gave them the same ssid and wpa key. The channels are 1 on router 1 access point, 6 on main router and 13 on 2nd router access point. Access point 1 is ip 192.168.1.1 and access point 2 is 192.168.1.2. Everything works fine when you turn it all on, devices get their ip address issued by the main router through router 2 and 3 no problems. The problem is, after about 6 hours the access points stop issuing ip addresses. Its as if they lose their ip lease from the main router. I changed ssid's across all 3 but same problem. My understanding was that as these were static ip's and outside the dhcp range of the main router there would not be a lease time. Restarting the 2 access points gives another 6 hours or so.....I might be missing something simple here. Im sure a switch would be a better solution but as always money is the issue here, any replies or suggestions are much appreciated