Mea culpa, Becca, I forgot your survey.  In fact, I forgot there was any
beyond the UNscientific (but quite large because it went over a long
period of time) survey I did of comparative life spans of ferrets with
neural crest markings.  Like your survey mine found very few ferrets with
neural crest markings reaching over late in the 6th year (a younger death
than the non-neural crest markings ferrets in the survey tended to have)
and a number of the standard health problems happened at younger ages.
 
One thing I think it would be interesting for someone to look at in
a scientific survey sometime is a comparison against controls for
cardiomyopathy type rates in ferrets with neural crest markings like
panda heads, blaze heads, and body spotting outside the norm other than
complete mitts with complete bibs (and maybe other than knee patches) .
In humans and some other mammals the rate is higher in those with some
types of neural crest genetic variants, especially for the harder form
to diagnose early (too often not spotted until symptoms become severe or
even until death occurs): hypertrophic cardiomyopathy.  I recall you
posting somewhere with some interesting research URLs about resulting
heart problems -- esp.  in regard to fetal deaths -- when the genetic
variant affects cells that occur early enough that the very early fetal
cardiac neural crest cells are altered rather than just the slightly
later neural crest cells, and somewhat recently (in months, I guess), a
member of the Ferret Genetics List, Silvia Pizzi, included a link to an
article on the increased cardiomyopathy rates with such genetics.  F-G
can be found at http://groups.yahoo.com/group/Ferret-Genetics/
 
Wolfy wrote as part of that post:
>But one thing that did stand out dramatically was lifespan.  If I recall
>only three ferrets lived past 6.
>
>Now of course that is one "snapshot" of a very small sampling and of a
>very narrow genre of ferret owners.  But I found it impressive myself.
>Of course on any other given time, I could find 10 people that write me
>that their ferrets lived much longer.  But at that given point in time,
>from that sampling, that was the finding.
 
It might take quite a LOT of time.  Over the many years since my survey
(with a number of later mentions of it) I still have only heard from
fewer than 10 people who had any ferrets with neural crest variant
markings who lived to be 7 years old or older, despite that still being
not in the least unusual and even still possibly the norm for ferrets
without neural crest variant markings.  (Of course, this post may bring
out more.)  In the U.S. one problem is that sales demand for these has
caused there to be a lot of carriers who lack the pelage changes due to
variable expression and perhaps at times due to genetic interactions but
some of these ferrets may have some of the health effects due to variable
expression.  I guess there have been something like 10 years (more?)
since there was the start os heavy selective breeding which greatly
increased the proportion of these genetics in the U.S.  breeding
population.  Bad situation.  Those ferrets were in greater demand due
to their appearance alone, and at first they also cost extra.  Selective
breeding gone wrong.
[Posted in FML issue 4870]