Is there any company that doesn't reserve the right to terminate a free hosted email account without notice?

If you want an SLA, you (almost always) have to pay for it. And if you pay for Google Apps, you also get phone support...

In the meantime: IMAP backups. If that's too much of a pain, there are also a ton of services (free or otherwise) which will do automatic backups for you, though you should really (really) make sure you trust them and their security procedures before you hand off access to your primary email account to them.