I tried to do the same during a bout of extended international travel. I popped out the fi sim once to try a super cheap local unlimited data sim (some countries are great for this), only to find out afterwards that it killed the fi pairing, and that re-pairing is not possible while abroad (tried VPNs etc., no dice). Your only method to get paired again is to either fly to the states (Hawaii), or to ship the phone to someone in the states and have them ship it back. Ended up having to go months without my main cell service, although months later it did somehow pair again while I was in Japan.
Keep in mind that you'd be just as out of luck if you wanted to switch phones while traveling, like if your primary was lost or stolen. For that reason, I canceled fi immediately upon returning to the states and strongly caution anyone I know against fi for extended travel.
Keep in mind that you'd be just as out of luck if you wanted to switch phones while traveling, like if your primary was lost or stolen. For that reason, I canceled fi immediately upon returning to the states and strongly caution anyone I know against fi for extended travel.