Google Reader thought me long ago not to depend or invest much time on Google services. Nowadays the only product that would cause me a huge problem if they decide to cancel it is Gmail.
Or maybe they'll cancel Gmail so users will transfer to (ew) Google Inbox. I sure hope not.
A long-term IMAP storage is legally needed for the spooks to read your email in real-time. With POP they don't have the legal excuses, so they cannot read it. Only what's left over there.
There is an API for that: https://developers.google.com/gmail/api/guides/push#stopping...