I can't answer about the age and size, but here in Puget Sound we used to
eat these when I was a kid.  My friend's mother made moonsnail hash, and it
was pretty good.  It took tons of pounding, though.  If people are eating
the snails, the odds are that the shells will be broken.  It is much easier
to get the meat out.  Also gulls will eat Pollinices, and on a summer low
tide some die from heat exposure.  I know of people who believe that
Pollinices decimates the clam and oyster populations, and will smash the
snails or toss them farther up on the beach.
> ----------
> From:         midgard[SMTP:[log in to unmask]]
> Reply To:     Conchologists of America List
> Sent:         Saturday, February 13, 1999 8:07 AM
> To:   [log in to unmask]
> Subject:      Polinices lewisii
>
> Dear All,
>         I recieved this inquiry about Polinices Lewisii, can anyone help?
>
>     "...how old do they get and how many years does it take to get about
> 4" in size.(that's about the size he is finding) He thinks people are
> picking the snails for food and he is finding the shells washed up at
> low tide."
>         Any additional information accepted. This is on Mudge Island,
> which is
> off  the east side of  Vancouver Island in British Columbia,  Canada.
>
>         Thanks!
>         Mariah
> --
> Mark and Mariah Lawson
> [log in to unmask]
> http://user.icx.net/~midgard/frntdoor/frntdoor.htm
> ICQ UIN 2128207 (Nick: Vigbrand)
> "Universe is not required to maintain a straight face!"
> "Smile! It no broke you face!"
>