I've never seen any info suggesting changing meta tags frequently. It is important to keep up with what search terms are trending, etc. but you'd likely be better off creating a page on your site optimized for those terms rather than changing an existing page. But changing for the sake of changing would be very risky and ultimately counter-productive. Google, etc. uses those tags as a beacon to tell them what your page is about but it still scans the rest of the page so if you're changing them and it's not reflected in the rest of the page, that's going to look funny to Google if that makes sense.
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