Steps to reproduce the issue

Have a Joomla site that is less than the current version; in this case, I have Joomla! 3.6.2. The current latest version is Joomla! 3.6.4. Have the System - Joomla! Update Notification plugin enabled.

Expected result

With the plugin enabled, I should be notified that an update is available, but not twice a day, every day. Perhaps once a week, or once a month, or once a week until I press a button to say, "I know, stop bugging me for this version."

Actual result

I am sent an email twice a day, every day — which is ridiculous — And, since I have at least 10 Joomla sites, I am receiving 20 emails a day — 140 emails a week, 640 emails a month nagging me to update.

System information (as much as possible)

Not relevant. These are all CentOS 6 sites running apache. This problem occurs on all systems, since it's a feature of your plugin. And I've seen other people having this problem, and even report it, only to be dismissed as a non-issue and closed. That is just not cool.

Additional comments

I have plugins and extensions that require cautious updating because I can't have my extensions break, and my site break just because I updated Joomla to the latest version, so I have to clone the site to a test server, update there, verify that everything works and then update the live site.

So, I can't update right when the new version comes out. I have to do it on my own time.
You have got to program your system to stop nagging me.
How about a little pull-down in the plugin that says "Once Only, Daily, Weekly, Monthly" so we can choose the frequency of notification.
Until you fix this, I'm going to have to disable the plugin... which I believe everyone else is doing given what I'm reading online. Isn't that defeating the purpose and accomplishing the exact opposite result you intend?