Here's another question I get asked sometimes, and since I received this recently, here's the answer.
Q: How long does it take you to do one of your books?
A: Well, I wrote the first incarnation of Jeweler's Apprentice February of 2007. I finished final edits and published it December, 2011. So that process took a little over 4 years. IT was tough, I thrashed out a lot of problems in my way of working, and basically finally got an understanding of "how to write a WHOLE book".
I started work on snippets that would be Traitor's Knife sometime during the final stages of JA, but didn't really start seriously on it until spring 2012. March, I think. Summer is always really busy, so I didn't get much done on it until fall again, when I set myself to diligently writing. I wrote the first draft that winter, (NaNo helped finish most of the big stuff!) then it went into edits immediately. Beta readers wrapped up on it that spring, and I released TK in July, '13. So that would be about a year for that one.
That was a very hard thing to do, but I felt like there were people waiting on me for the next book, so I really felt pressure on making sure it got out as soon as possible.
At this point, I'm letting my brain rest a bit, and haven't made any solid plans for when the next in the series will be out... just letting the ol' creative muscle off the hook for a while.
I definitely think that the first book or so is the hardest, since you don't know "how to write a WHOLE book!!!"... and that the more you do that, the better you'll get.
(I may even go so far as to recommend first-timers write 2-3 books before they take a swing at publishing. If you build buzz for the first book, it's easier to have 2nd & 3rd ready to release in sequence, instead of having the pressure to write it from scratch. That, and it's easier to promote when you're thinking of several books you have to sell, instead of putting all the effort out there for 1 single book available.)
Also, once you've written that many books, it gives you a lot more confidence to be able to make decisions on how many books you are able to release on what kind of a schedule.
And you'll learn tons on those first few books, and you can go back and tweak the first one with what you learned on the second.
Each book is hard in it's own way, so I understand authors who say "It never gets easier."