I totally agree with you: I have Evernote for Business with 9 subscriptions that just got auto renew all at the same time (even if there were not created at the same time). No warning, no pro rata. I had a reminder on my todolist on may 29th for 1 account, and the rest of the reminder in june to every date they were created. I was ready to renew, but not 9 all at the same time.
There is convention in the auto-renewal world, and Evernote should definitely join it!