Yeah, but you're talking a military facility - not (like you're seeing in most of those watch schedules) a ship at sea, or some other location where there's always gotta be X, Y, and Z at hand on the P, D, and Q. If you're talking actual watches, I'd posit/recommend four shifts of six hour watches, with each shift doing an additional 2-4 hours worth of some sort of activity or maintenance either (consistently) before or after the shift, making them available if the feces meets the rotating turbines. As it is, though, you've got only 30 people for your watch setup; this isn't a military installation, it's a dinky facility somewhere. It might be a black facility, but it's frickin' podunk, three buildings max, with at best 15 guys walking beats and supervising the gates for 12 hours a day.
In any case. In a multi-building facility, you aren't going to be able to have an 'inside patrol' and an 'outside patrol'; you'll have guys moving through each building, keying into 'watch points' either with a designated route, at designated times, or - if they're smart - going erratically from one to any one of several others within range. You might have guys doing an hour on the cameras, then rotating out to do some walking, thereby always keeping someone fresh with an eye on the screens.