Sounds to me your running out of IP addresses because of the IP address lease time value which may not be configurable.
A lot of routers have a subnet mask of 255.255.255
.0 (aka CIDR /24) which means you get 255 IP addresses (e.g. 192.168.0.1-192.168.0
.255), if you can find a router that supports a subnet mask of 255.255.254
.0 (aka CIDR /23) you will get 510 IP addresses (e.g. 192.168.0.1-192.168.1
.255) or if that's not enough try a router that supports 255.255.252
.0 (aka CIDR /22) then you will get 1020 IP addresses (e.g. 192.168.0.1-192.168.3
.255). Alternatively try to find a router that supports configurable lease times for the LAN / WLAN and set it to a very short period.
Sorry cannot recommend any products as I'm retired now and not up to date with what's now available.
Edited by dect (Sat 12-Jan-19 16:02:40)