Bing: Use 302s For URLs That May Change In Two Days, Otherwise Go 301

Fabrice Canel from Microsoft Bing said on Twitter "preferable to use a 302 redirect if your destination URL may change within 2 days, else 301 is recommended." So if your redirects will be in place for less than two days, go with a 302 - otherwise, Bing recommends a 301 redirect.