In a way, I'm glad that Vanguard will end, meaning that it can actually have an ending. I love Vanguard, I've only started reading it in 2011, and I'm already re-reading it so I'm fully charged for the last novel. Vanguard changed TOS for me, showing there was far more to the 23rd century then just Kirk and co. Great writing, good drama, fantastic characters, witty humor, terror and angst, action, heroics, romance, even some courtroom drama and some glimpses into colonial life in Star Trek.
And what I feared the most, was that it was going to get dragged along, stretching it out over to many novels, putting to much in there. Ever since Open Secrets, there has been this unnerving feeling of things building up to something terrible and dangerous, building suspence. If that was dragged along to long, it would have become tidious. What direction will you go with the characters to keep them interesting? What sort of plots twists are you forced to put in there to keep the story going?
No, better to end it on a high, with an ending that will leave us both wanting for more but also satisfied. I, for one, can't wait to read this final installment, even though it means it will be the end of one of the finest moments in Star Trek, called Vanguard.