Unique Visitors Counter broken

The "unique visitors since" counter on our website has stopped counting new visitors. Instead, it is decrementing by an average of 1 per day. This has been going on for at least 3 months. Our Google Business Profile shows a healthy stream of visitors, so it's not a lack of same causing this problem.

hinoonhsv.toastmastersclubs.org/
Club 3963
John Williams, site admin

The websites you folks provide and support are great asset to Toastmasters everywhere.
Thanks for all you do.
 

The counter rolls over the last year.  You've probably had fewer new (unique) visitors this 'period' than you did for the same period a year ago.
You can reset the counter 

Pam is correct.  The thing to understand here is that the "unique" criteria puts a burden on our database because the only way to verify that a new visitor is "unique" is if we store the IP addresses and/or device ID (the random text id we put in a cookie on your devices) of every unique visitor in our database so we can use that later for checking "new" visitors.    

This means we have a massive DB table that just stores a bunch of IP addresses and/or device IDs.   

This table size was getting out of hand, so I had to make a decision in the past that like a lot of features we have in FTH, we will give you the feature, but often with certain practical limits.  In this case, the "limit" was the time frame for which we will keep the IP addresses and/or device IDs so that we can keep the related table to a sane, manageable size.

Steve, is the DB able to keep up with a year's worth for all websites? If not, is there a shorter span that we should use?

A year's worth seems ok.