Unfortunately there is no maximum or minimum time between audits. One reason for the second audit may very well be that they found something in the first audit that triggered the second one. So it would be a good idea for you, or your tax professional, to study the audit report of the first audit to see if there is anything in it that would trigger the second audit.
And the IRS can decide to audit you personally while they audit your business. As in the case of the second business audit, there could be something they find in the business audit that makes them suspicious of the personal return.
If you have been having these problems, you would be well advised to hire a good tax professional to help you with your next returns so that you don’t trigger yet other audits.