After all travel is over is best, since there are some implications from (e.g.) cancelling a trip altogether - this is more about people trying to get refunded for downgrades though, to take one example of many. In a sense it's perhaps immaterial since it is sometimes taking a while to process a claim in many cases (but not all), so even if you did claim immediately it will only get looked at after you get back. So I wouldn't want to think this is an important factor for Right to Care expenses, it may not really matter much.