Not a DD-WRT fan, using HyperWRT.

the timeout and delay when accesing the admin page (and other surfing activities) is caused by a limitation due to the implementation of linksys routers. linksys is known to have long timeout for IP entries visited. in order to shorten the timeout, one would need a startup script:

echo 4096 > /proc/sys/net/ipv4/ip_conntrack_max
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts
echo 1 > /proc/sys/net/ipv4/icmp_ignore_bogus_error_responses
echo 512 > /proc/sys/net/ipv4/neigh/default/gc_thresh1
echo 2048 > /proc/sys/net/ipv4/neigh/default/gc_thresh2
echo 4096 > /proc/sys/net/ipv4/neigh/default/gc_thresh3
echo "600 1800 120 60 120 120 10 60 30 120" > /proc/sys/net/ipv4/ip_conntrack_tcp_timeouts

not too sure if DD-WRT supports startup script, anyway if it doesn't, try HyperWRT, u'll be able to find it in Sourceforge.net, the popular open source community.

or get a WRT54GL... that's a "rebadged" version v1~4 WRT54G running Linux based system.