Seek and Destroy means that the group will run around a certain area for a certain time. The area (and possibly the time) are determined by the type of units: choppers search a bigger area than infantry.
After a while they will get bored and stop, so you need a cycle waypoint as well if you want them to do it for ever.
I recommend you have switch some of your groups into guard waypoints rather than S&K.
I also
very strongly[/i] recommend that you playtest, playtest and playtest until you get the result you want. Try it out from different points of view. Check
this tutorial for a few tips.