Use cert bot to auto renew https://certbot.eff.org/docs/using.html#renewing-certificate...

Also include command like below as part of your automated audit scripts:

echo | openssl s_client -connect google.com:443 2>/dev/null | openssl x509 -noout -dates

http://www.shellhacks.com/en/HowTo-Check-SSL-Certificate-Exp...