Napa and Sonoma only? That's is true anywhere, I think.
According to this article from Liz Thach, it is not all about to chase new club members, but also it is a matter to retain them.
This is nothing new as all retail store face the same issue as I learn when I was working for Nordstrom.
How to retain customers when there are so many choices?
The answer is to keep the customer interested with discounts, events, news letters, several shipments a year, and wine choice flexibility.
Little gifts can't hurt, I'll add but it is not allowed in all states.
References: https://www.winebusiness.com/news/?go=getArticle&dataid=192707
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