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A 302 is designed as a TEMPORARY redirect. How temporary? I like to think of it in terms of hours. That makes it a lot clearer when thinking "how long is too long". For the most part, 302's should not be used. There are some corner cases where a 302 is the best solution, but in my experience most of the times 302s are implemented inappropriately and should not be used. A 302 is harmful to your rankings as it prevents your PR from flowing naturally throughout your site. If you are using a 302 for internal linking, you are definitely damaging your SEO. For external links, a 301 is used when the content has been permanently moved to a new location. I am a bit confused regarding your implementation of a 301 for a "buy now" button. That sounds more like a direct link, and I am not clear why a redirect is being used. A final point. Affiliates pointing to their master site should use nofollow links to be compliant with Google's policies.