Is there alot of "traffic" on the network while your doing these tests? bascailly what happens is... anope sits and waits for traffic, when it gets some, it checks if any timers need to be executed, if they do, it does them, deals with the traffic, and then returns to waiting for traffic. In the event your the only user on the network, there is a strong chance very little traffic is actaully being sent to services, as such, the timers are not accurate. You can test if this is the case by simply doing a /msg nickserv help every few seconds and see if it improves the accuracy of the timers.