…anyway, just to share you based on my experiences, certification audit is around 2 to 3 days (to audit the entire system)… surveillance is 1 to 2 days (since it is usually not taking account the entire system), and re-certification is the same as certification audit (since they need to audit again the entire system)…
…but then again, your organization and your chosen certifying body should agree on audit plan for this purpose…