This is always a tough question to answer, but I'll give it a shot based on what I've
observed as a knapper.  
My opinion is that there are several qualities or elements that
affect how fast a knapper learns the art of flintknapping as well as how far they will
progress and to what level of skill they will progress to.

Element #1 Hand-Eye Coordination

   Much of the ease of picking up flintknapping has to do with good hand-eye
coordination.  Success comes to the knapper that can strike an area that he or she is
aiming at.  Failure and frustration plagues the knapper who failes to strike his or her
chosen area as that is where breakage, hinges, stacks, and many other problems can
originate.  So I believe that there is a physical coordination base element involved.

Element #2 Practice, Practice, Practice..........and.......Practice

Over and over again, the quality possessed by knappers who have learned
flintknapping quickly and progressed quickly,  is that they would spend hours EVERY
night and hours upon hours every weekend flintknapping.  The more you knap the more
your brain records and ingrains the methods and techniques.  Something else happens
too, you make mistakes and correspondingly learn how to fix them by trying new methods
and discovering new tricks.  Flintknappers like
Woody Blackwell and Mike Santiago
rose to excellent skill levels in just a few short years by investing huge quantities of time
practicing.  Most knappers probably do not knap every day.  I knapped many days per
week in the beginning, but knap once or twice a week now.  You will go through huge
amounts of raw material practicing, therefore I recommend using renewable lithic sources
like toilet tank lids (Jonstone) and glass bottoms of jars to supplement your good rock
supply.  I still have some
points made from Jonstone that were created in my first couple
of years of flintknapping.

Element #3   Artistic Abilities

  Some may argue with me on this element, but I've watched flintknappers who have
been knapping for a decade or more and their points just never progress beyond a simple
tool look or field grade look.  There is absolutely nothing wrong with that, as those
flinknappers have simply reached the ceiling of their elements and are quite content and
happy staying at their particular skill level.  I've also taught a few beginners and noticed
that those who already do other artistic things like painting, drawing, writing, wood
carving, sculpting, etc. seem to have an eye for balance, shape, and flake scar patterns
that help them progress faster than those that do not have the artistic inclination.

   I do not believe this artistic ability affects
how a knapper flakes his stone, but will affect
how a knapper chooses to take off strategic flakes from his or her biface.  A nonartistic
eye would remove flakes out of necessity in order to shape a tool for function, while the
artistic eye shapes the biface for function as well as eye pleasing form (e.g. opposing flake
scar patterns, symetry, typology correctness).  The more artistic you are, I believe, the
more likely you will be to progress to the tops of the flintknapping art.  The only exception
to this that I've observed so far seems to be those individuals that are excellent carpenters
and machinists.  Those talents, for an unknown reason, also lend well to developing good
knapping skills.  Perhaps it's that excellent carpenters and such connect with that same
right brain ability as artists.  I'm no psychologist or doctor, so I'm just taking a wild guess
on that one.

Element #4 Availability of Raw Materials

   When a knapper lives close to a source of good chert, he or she has an almost
unlimited supply of stone to practice knapping with.  So this element ties in with element
#2 in the aspect that the high availablility of raw materials allows the new knapper to be
able to afford to practice more with good materials.  When I was in my first couple of
years of knapping, I couldn't afford to buy a lot of stone, so this forced me to knap less
and to be more cautious in how I knapped so as to avoid as much waste through
breakage as possible.  While this small quantity of raw materials allowed me to develop
an early respect for stone, I also believe it slowed my progress.  The first year I could
afford to buy a bucket or two of good rock, was the year that really helped me progress
by leaps and bounds.

   Knappers have a saying "Make it or Break it", and what is meant by this is that if you
are afraid of breaking the stone, it will impede your ability to complete the point you
intended to knap, so go for it even if you break it..  Having access to a source of
I've progressed quickly in learning how to knap it as it was of minimal cost to me.  I do
still hate to waste good stone, so even when I break bifaces of "free" rock, It still bothers
me, I just think I get over folding the piece a lot quicker knowing it only cost me my time
to go get it.

Element #5 Access to Other Flintknappers

If you can knap regularly with experienced knappers, you will be able to watch them
knap and be able to ask their advice when problems arise with your own knapping
project of the day. Watching an experienced knapper reduce raw material to finished
points is one of the best ways for beginners to learn the techniques of flintknapping.  I
unfortunately did not live close enough to any experienced knappers to take advantage of
their regular teaching when I was a beginner.  Some of this was a lack of knowing local
knappers.  I was able to eventually learn much form the likes of
Jim Redfearn, D.C.
Waldorf, and Craig Ratzat.  In fact, I used to get lessons from them any day I wanted
because I bought their video tapes.  For the new knapper who lacks access to
experienced knappers, videos can be a great substitute.  As you watch and rewatch these
videos, you will see something new each time.  As you progress in your skills, you will
find that you can refer back to these tapes to watch for specific skills that you are looking
to master (e.g. billet selection, striking angles, and platform prepartion)

   Now that all that is out of the way, let me see if I can tie it all together and actually
answer this question.  It has been my observation that master knappers have high degrees
of all five elements and tend to have learned very quickly.  Knappers below the skill level
of the masters may progress to be masters some day, but will have strong elements and
weak elements that make-up their skills until then.  For example, knapper "A" may have  
high elements 1,3, and 4, but low elements 2 and 5.  Knapper "A" would likely fall into
the intermediate level of knapping ability.  If knapper "A" makes more time available to
knap (element 2) and attends a few knap-ins (element 5), his or her skill level will likely
rise along with the quality of his or her knapped products.  If the knapper posesses all the
elements it may take as little as 3-6 months to knap an acceptable replica of an
arrowhead.  However, a knapper with fewer of the elements may take up to a year
before he or she is able to knap an acceptable arrowhead replica.