How much do artists draw in that sketchbook over the others of yours?

At least from what you're posting, it doesn't sound like a whole lot...

Some of it depends on the convention ("Plush" gets used more at non-furry events), or the artist (plushes are inherently less realistic, so I wouldn't suggest it to Dark Natasha for example), or what other things interest me. "Now We Are Plush", "Soaking Wet", and "Wumpus" are my three oldest, still active con sketchbooks, and they don't come out as often as the used to.

I do tend to lean more towards loose-sheet commissions these days.

I seem to recall you mentioning not being able to get particular commission styles due to the relevant book being with another artist, so separate sheets makes a lot of sense. =^.^=

It also avoids the potential risk of losing an entire book due to mishap.