How long should I wait for rich snippets to appear in Google?

There is no universal answer to this question as it depends on many factors, for example, how often your site is crawled by Google.

Once you’ve enabled rich snippets for your store, check them in Google Data Highlighter. If everything is ok, you will need to wait for Google to re-crawl your site and understand the markup found there.

See more details on Google Rich Snippets page
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