For the most part, I agree with Les. I don't much like splitting parts just to split them up.  However, if you're sure an area needs more detail than the area provided in a continuous pelt, than you should split it off. One thing - at lest for me - is I like to keep all my textures on one map. Two at most. I don't get to keep things that simple  often enough though in my day job.

So anyway, think about an area's overall importance, then consider the impact splitting important areas will have on creating seamless maps. If you find the area really needs its own map or to be broken onto a larger area on the same map as the rest, do so. Every model is different and every model requires a slightly different approach to uv mapping. However, for creatures and humans, pelt making makes the most sense (but the model may fight you on it).