I've been keeping track of the time it takes me to spin 100 grams of singles so I can get an idea of just how long it's going to take me to spin enough yarn for a sweater. It's not nearly as bad as I expected.
I spin about 32 grams of singles in an hour, or about 100 grams in 3 hours (I weighed the fleece and clocked how long it took me to spin it).
But how many grams do I need for a sweater? According to my very handy The Knitter's Handy Guide to Yarn Requirements, for a sweater with a 40" circumference, I'll need about 2088 yards of sport weight (knitted a 6 sts/inch) or 1475 yards of worsted weight (knitted at 5 sts/inch). Based on the yardage reported on ball bands of wool yarn, sportweight yarn has about 300 yards/100 grams, or 3 yards/gram; worsted weight has about 200 yards/100 grams, or 2 yards/gram. That means that I can divide 2088 by 3 to give me the number of grams of sport weight I'll need (696 grams) and I can divide 1475 by 2 to give me the number of grams of worsted weight I'll need (738 grams). Given my spinning rate of 32 grams/hour, that means that it should take about 22 hours to spin enough sportweight or 23 hours to spin enough worsted weight.
Of course, this doesn't take into account the time it will take to ply the yarn, but that part goes pretty fast. I think it's fair to estimate that I can produce all of the yarn I need in less than 30 hours. That's less time than it should take to knit the sweater! Until now, I thought that spinning would take twice as long as knitting (I also foolishly thought that knitting was more enjoyable than spinning). Now my curiosity is sparked--I plan to clock my knitting time, too, so I can compare the two.
In any case, I'm going to get about 30 more hours of pleasure out of this sweater than any I've knitted before!