The indicated flight ended in Frankfurt, where we transferred to Flight 308 to complete our journey to Florence. The Lufthansa Business and First Class lounge in Boston was very nice, and provided an excellent lunch as we awaited our 5:05 PM departure. There was a delay in departure due to a minor issue, but the flight arrived early in Frankfurt. As for nearly all flights to Europe, this one is overnight, arriving at around 7:30 AM local time (scheduled for 8:00 AM). The cabin crew was outstanding: attentive without being intrusive, friendly and promptly responsive to every request or question. The service in business class is individualized to a fault: if carts were used instead of individual trays, dinner would likely proceed more quickly and offer the opportunity for more sleep in the very comfortable seats, which recline to flat.
When we arrived in Frankfurt, there was a very, very long walk needed to reach our transfer gate, which initially we found unpleasant. But after hours of having been seated or sleeping, such an extended period of walking was probably quite healthy.
Our return flight was equally good (flight LH 9439 to Munich and then LH 424 to Boston). It was entirely during daylight, and the slower meal service mentioned above was more pleasant to experience, with plenty of time left for a nice nap to ward off jet lag.