2 Rules of Thumb

1.) One can expect a talented, careful production worker to make a serious mistake at least once in every million operations. 

Thsi means that a careful production spinner doing 3 operations per minute and working 3,000 hours per year is going to make a serious mistake at least once every 6 years.

If that mistake is dropping the stone spinning whorl onto the stone floor, then we can expect that mistake about 5 times in a 30 year spinning career.  Thus, we can presume that plain stone whorls were used for production spinning because they were very likely to be broken or lost every few years.  From this we can deduce that a spinning whorl found as grave goods was used for production spinning for less than 30,000 hours. This would be only about one-third of a production spinner's career.  A production spinner that has already broken a few stone whorls, knows they might break another whorl. Thus, they use a plain whorl for their production spinning. 

We can also deduce that a rich  lady spinning carefully for 2 hours a day, could use a single stone spindle whorl for all of her life without loss or damage - but that whorl could not be presumed to be the kind of tool used by commercial production spinners.  She could do that valuable whorl because she was less concerned with her production rate and thus could be more careful and protective of her whorl. She was a hobby spinner.

2.) It takes about 5,000 hours to learn a complex manual skill such as playing the piano, surgery, or spinning.

Practice the skill for 10 hours per day and it can be acquired in 1.5 years. Practice for only 2 hours per day and it takes 9 years.

Stretch the learning over 9 years, and old skills will be forgotten as fast as new skills are learned and true mastery will never be achieved.  A musician will practice 4 or 5 hours per day, part of which is learning new skills, and part of which is reviewing and renewing old skills.  A spinner that does not go back and  review and renew old skills on a regular basis will lose them. Two hours of spinning per day is not enough to maintain professional level competency in hand spinning. If you want to be a good spinner, you need to practice 800 or more hours per year.  

From this we can deduce that the spinner carefully using a valuable, highly decorated stone whorl for only a couple of hours per day is not a competent, professional spinner.  Valuable, highly decorated stone whorls were stores of wealth - jewerly - not the working tools of a competent, professional spinner.  They had to be treated with more care than the plain stone whorls of the professional spinner.

Prior to the the use of metal spinning tools we know that production spinners had sets of stone whorls for spinning different grist yarns, and that the typical dimensions/weight of  the various standard stone whorls in a community often remained fairly stable for hundreds of years.  Even in the stone age, professional spinners had professional tools.

And, the professional production spinner was likely to use metal spinning tools after 1,000 BC because they are much faster.  We do not see them for 2 reasons.  1) Metal was valuable and could be resmelted.  Any worn or damaged metal object would be resmelted.  If the valuable metal was going into a grave, it would be resmelted into jewerly.  2). We do not recognize them for what they are.  

I took my hand made knitting sheaths and  needles to some important archaeological sites where I thought knitting sheaths might be found.   None of the staff archaeologists on site recognized them for what they were.  All of these sites had an lot of "broken awl points" that they had not checked for the wear marks of a DPN used with a knitting sheath. A DPN used with a knitting sheath develops a curved wedge shaped point. And, eventually the needle fractures at the point where it is stressed by the knitting sheath. To the naked eye,  the broken piece looks like an awl point.  

I have no doubt that if I took my latest drop spindle to a bunch of staff archaeologists, they would not recognize it as a drop spindle. In fact, it is a "twisty stick". Alden Amos, supplies them with his wheels for testing the quality of fiber.  It is an old and common tool.

However, if you are seated and use your (metal wire)  twisty-stick with a thigh roll, it can insert a lot twist very fast. If you draft long draw with one hand and roll the twisty stick with the other hand, the thigh roll  forward can twist the make into competent yarn, the drafting hand can be dropped, and the thigh roll backwards can wind on the yarn. There is no wasted motion with either hand. This makes me think that some of the historical descriptions (Bronze Age Greece) of  spinning yarn by rolling it on one's knee or thigh may actually have been the high speed production of woolen yarn by use of a twisty stick, while drop spindles with whorls were being used for making worsted yarn.   A supported spindle will produce a finer, more consistent yarn, but the wire twisty-stick with thigh rolls using both the forward and backward motion is faster.  Nobody does this kind of spinning any more. It is very much like patting your head and rubbing your tummy at the same time, but it can be done.