The timer is no problem at all for attackers, if they actually attack.
The timer is a problem for the attackers, even if they do attack, if the defender has too many troops. Right now it seems like the timer is capped at 2hours, no matter how many combatants.
There are 7200 seconds in 2 hours, and only 1 respawn per sec per team. As a result, you can't defeat armies with 7200 troops without capping their spawn. And an army as big as that will most likely fight back. Making it pretty much impossible to kill 1 player per sec for 2hours non-stop.
In this battle the attackers were forced to kill 1enemy every 1.5 sec.