The first book is, as is often the case with a series, seemingly the most inventive. There is so much novelty there, and the scope is grand, following the Company through numerous situations to the final battle at Charm. There seems to have been no thought given to sequels; just an attempt to capture a slice of time in a unique world, and fill it full of interesting characters and moments and details.
The second and third book, too, give little thought to a larger arc. The fourth--not really. But the last six books--divided into a set of two books and a set of four--he mapped out a more-planned story (although it appears he changes his mind about some major issues during the second series, so he may have not fully worked it out in the first pair), and leaves major plot threads hanging from one book to the next.
And by the final book, Soldiers Live, he brings unambiguously into focus the central theme of all the books--mortality, and what people will do to avoid it--as we see the last surviving member from the first book, a character we've come to know very well over the space of ten books, and a final conclusion that is just fitting and perfect--and would perhaps seem far less significant if you hadn't read the whole series and known the character so well.
This is what fantasy should be. It makes me embarassed it took me this long to stop reading the stupid Robert Jordan novels. (I gave the most recent one a miss, finally.)