It's not a matter of a set time but more a matter of the number of books that have been bought. They have to have a number of books bought in common before they'll list it, otherwise it can literally stay as also-viewed for weeks or even months.
Case in point...Short & Sweet had sold a whopping 15 copies in its first 3 weeks of life, and then had a successful free run in which I gave away 5679 copies in the US. I only had also-vieweds for 3 weeks and then boom! They immediately became also-boughts on like the second day of the free run.
On the other hand, when I sold strong right out of the gate for one of the Dani books, they flipped form also-vieweds to also-boughts in like 3 days.
Generally the alsobots crunch on Thursday and Sunday. Then, I *think* you have to sell a certain number of books before the "boughts" crunch in. My guess is that the sales threshhold is 10. And that is probably a threshhold between crunches, not an aggregated total. An aggregate of 10 likely gets you the Also Vieweds.
But that's during a normal cycle. There have been some abnormal cycles as we neared the holidays. And a couple of months ago there was a horrible 12 days or so when no crunch occurred and no newly pubbed books got them.
Phoenix is wise. The system is very bogged down right now. I sold nearly 200 copies of my boxed set on Christmas Day and it literally took the entire day before I saw any of that reflected in my ranking. So I suspect things are just taking longer than usual to update, sales rankings and also-boughts included.
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