I was only able to check the bag to FRA because of the 12 hour rule. My flights were 13 hours apart. United only allows layovers of 12 hours for checking bags. At least that is what I was told. LH in Prague tried to check me all the way thru and was unable to do so. Asked UA when I checked the bag in the morning and they told me it was because the flights were over 12 hours apart. Had to get the bag in FRA and bring it back to the airport after my overnight stay at the Hilton.