You can specify how long a visitor is allowed access to your Cloudflare site after successfully completing a challenge (such as a CAPTCHA). After the TTL has expired the visitor will have to complete a new challenge. We recommend a 15 - 45 minute setting and will attempt to honor any setting above 45 minutes. You can get to the Challenge Passage TTL option by going to the Firewall app
Note: The Challenge Passage TTL does not apply to challenges issued by the web application firewall (WAF) as these challenges are triggered by actions taken on a domain, and not based on the visitor's IP address.