Let’s Encrypt CA issues short-lived certificates (90 days). Make sure you renew the certificates at least once in 3 months.
In practice I think many folks set their cron job to run as frequently as once a day or week. Make sure once every 3 months is your lower bound.
When the renew command is used Certbot will attempt to renew any previously-obtained certificates that expire in less than 30 days. If your certificates don't expire for more than 30 days nothing will be done so it is totally OK to run daily