Can't really answer from the slave's standpoint, but I can share my own experiences with my own slave.
This girl was on the personal chain of a VERY rich slaver. He didn't make any real demands on her, and gave her the bare minimum of rp to get her installed as a house ornament. Basically, she was bored as hell. So I borrowed her a few times and made her into a pack mule on my various trips to different places. Eventually, we worked out that I would buy her, but the slaver was quite jealous of his chain and priced her out of pretty much anyone's reach, even though he didn't do anything with her (Status symbol perhaps? blah)
So I starting digging around in some oh his shadier practices and exposed them, whereupon he pretty much gave her to me to shut me up.
I am of the warrior caste, but am not rich by any means. I live in a yurt by the river LOL. However, I am out and about all over the place, constantly keeping busy in my quest to fulfill my warrior duties, make a bit more coin, competing in tournaments for the honor of my homestone, and just generally keeping entirely too busy. And now I get to drag her cute blonde ass around with me for everything. She seems to be far happier, as she doesn't get to get on SL as much, and I'll keep her well-immersed in rp, even though I may not be the best of para-rp'ers. At least I can give her something to do...