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I guess it depends on which casino you're following, but most of the time whenever a ToS is updated the pages will show the edited time, plus some businesses send e-mails whenever their privacy policy is updated. Building a bot to track if a ToS page is changed is also good though, even though I'm not sure it will be useful for a business that regularly sends info whenever their policy is changed.
Good thing if they would really be mindful on sending out those via email alerts into their users but not all would really be that reading up their emails on which it would really be that still that likely be useless on this case. It would be better that they would be making out that kind of alert or pop up instead.