The standard doesn't simply require audits to be conducted. You asked about how far apart audits should be. The ISO 9001 requirements require your audit program to be based on other things, not time "between" audits. If you are simply doing audits because ISO-says-so, then you are missing the point. If this is the first time you have done audits, compliance to the standard is a reason, but you could do an audit/day until you cover all requirements.
Let's go back and ask the same question. "Why are you auditing?"