Agent takes a long time to negotiate and absorb this initial load from the server - more than 15 minutes, if I recall correctly. After it has done so, dropping the outdated sections is no problem.
There wasn't a way of telling it to ignore anything more than x-days old, last time I looked.
It's usually more trouble than just one thread is worth, but then, some people do seem to have an excessive amount of time on their hands....
RL