Just like Troll goods are best goods. Free promotions... they are very useful tools to help generate interest and sales. For a great example: me. Heh. As you guys well know, I have been out of writing for a little while. Where once I pushed out two stories a week (often over 15K for at least one of them, and generally over 30K total wordage), now I'm down to barely one. Barely one. My schedule's changed, my days off have changed, my work routine has changed, and while I am writing this AT work, it's still much busier than my old job. Hence, writing time has cut down while I try to rebalance everything.
What does this have to do with free days? Why, let me tell you. Since I had been so out of the loop, I decided to put the first of the Dominating series on a free promotion over last weekend in order to generate some interest in my other titles, and hopefully keep my name out there. It was only two days, but the very next day, my sales/borrows spiked. Granted, I would use them sparingly, but in this case, it worked wonders.
In many cases, putting the first of a series out for free when you publish a new one in that series will help generate interest in the sequels. If they liked the first one, they may go ahead and borrow the second, or third, and so on. It can help generate interest in related novels as well, and bundles. When I get the third (and last) Cheri book out, I am going to bundle all three up, wait for a couple days, then release the bundle as well at the same time as a free promotion for the first book. I want to make sure all the backmatter is updated in the old Cheri book to have links to the new one(s), hence the wait.
In the meantime, I'm going to bang my head against the table over lazy maintenance men not wanting to come in to fix a problem at work. I tell ya what, one of my next Dominating books is going to be "Dominating Her Plumber". I SWEAR. :)