You don’t need a permanent COO to succeed.
Fresh ideas and skills drive change and are likely the very reason you hired a COO. Their job is to systematize, automate, and ultimately make themselves dispensable.
By the end of their tenure, your company will be in a new state. An interim COO lets you ask: Is this the right person for the next phase? If so, renew. If not, plan the handover.
Six to 24 months is plenty of time to make an impact.