You can theorize and try to predict all you want, but the wait times are never going to be consistently right.
You get one large group (BTG's, Marching Bands, Cheerleaders, etc) that travel as a set of larger groups and your 5 minute wait is now a full queue.
Back when Pandora opened, I forget which ride it was, but someone actually had the empty queue time clocked at like 8 minutes or something to get through. So, think about that. A 10 minute wait could actually be a walk-on, it's just that the queue is that long to get through. I know that Finding Nemo is a pretty long queue and a 10 minute wait is a walk-on.
So the math geeks and theorists of the world can try and do this, but there's so many variables that it's nearly impossible. I just check in when I'm around those areas and if it's worth it, I'll get in line or see if I can snag a FP.