In reply to Peter.

I filed a ticket to clarify this an hour ago and still have seen no response. Not great service if a question about their plans takes more than an hour to resolve.

I did find this on their forum: https://community.sendgrid.com/sendgrid/topics/will-free-account-expire

So it look like I'll switch to something else, either their lite plan or Mailgun. Mailgun looks good, but the DNS changes make setting it up much more work. I do however like the parsed incoming mail support as well as SMTP.