SSL renew or install automatically?

wackyblackie answered you because I was offline (time difference)

One of the advantages of a self-signed certificate (+ CF) is that it is valid for 10 years and then you don’t have to renew the certificate every now and then.

But okay since I see that you intend to sell something on the site
then full strict mode has more advantages especially when integrating some third-party payment services, etc. into your website.