Exactly. If you've got a head for remembering Latin, i.e. is id est, so you can try swapping "that is" into the sentence to see if it sounds right.
E.g. is exempli gratia so you can try swapping "for example" in for the same trick.
If you forget, avoiding the abbreviations is fine in most contexts. That said, I'd be surprised if mixing them up makes any given sentence less clear.