Earlier quoted context omitted.
I appreciate what Let's Encrypt is doing, and have even donated, but internally at our org (as a DevOps), I cannot sell certs that expire every 90 days; $300/year for a wildcard cert is a small price to pay for 1 year expirations.
I think LE's 90-day expiration reason #2 is really the key: encouraging automation. So what it really is investing effort once and working for arbitrarily period of time. If the TLS certificate renewal process cannot be automated but must be manually done for some reason, that perhaps LE certificates are really not what you are looking for.
With that said, still a big supporter of Let's Encrypt for folks who can tolerate the constraints.