Spinning Singles

I have been spinning on the singles that I will cable, so I thought I'd show them to you. This is 70% Merino/30% Kid Mohair and I'm spinning them in a laceweight. I'm going to spin four bobbins of singles, then ply them together in twos, then reply onto my giant plying bobbin - I think. This top is very soft and its almost pure white, but I feel like I'm not quite getting a rhythm with it. I seem to either be treadling too slow or drafting too fast. I've got the whorl set at the highest ratio, but I guess as slippery as the fiber is, I just haven't figured out exactly how to get this spun. Because I feel like I'm not quite getting it (its getting spun, I'm just not relaxing while I spin it, which pretty much defeats the purpose of spinning), this is the first bobbin. At this rate, if I don't get the hang of this soon, I'll be spinning this until Christmas. I've also discovered that I spin more fiber, faster when its colored. I love the natural whites and creams that grow on the sheep and other fiber critters, but spinning colored top or roving seems to keep my attention better. I guess its like knitting with variegated or tweed yarns - you keep going because you don't know where the colors will land next.

On a completely non spinning note, I have a question. A couple of years ago I made some felted slippers from Brown Sheep Lamb's Pride Worsted (they aren't the Felted Clogs, but they are a Fiber Trends pattern). They wore out at the end of that Winter. Since just about everyone who has ever picked up a pair of knitting needles has knit these (if you haven't you really should - they also make great gifts for men - Mickael lives in his), what are your favorite yarns to use for them? What seems to last the longest?