I am flying Dulles to Frankfurt and Frankfurt to Florence next week. All ticketed through United although I will be flying Lufthansa. I have my seat assignments for the Dulles to Frankfurt leg but lufthansa and united are both telling me that for the flight from Frankfurt to Florence they don't do seat assignments ahead of time. The lufthansa rep told me I will get a boarding pass at dulles but I won't get an actual seat assignment until I get to the gate in frankfurt! Does this sound right to you guys? Thanks!

Yes, this sounds right. I flew on Lufthansa through Frankfurt to London, and that is how it was handled. In fact, every time I have connected in Europe on any airline, the intra-European flights did not assign seats in advance.

I agree; happens routinely in this sort of situation and even if it didn't (undoubtedly somebody will pop in here and tell you about their Aunt Mabel and how SHE got HER seats) there's little you can do except check in for the Florence flight as early as you can once you reach Frankfurt

Thanks! We have about 85 minutes from the time we land in frankfurt to the time of our flight to florence. I hope we can get through the passport controls and on the gate fast!

That's not my experience. I have taken a number of connecting flights from Frankfurt on LH and every time I was given a boarding card with seat number on. And when my luggage is through checked, I get the second boarding card when I check in for the flight to FRA.
You can only request a seat in advance for long-haul flights, not intra-Europe.

You shouldn't have trouble making the connection in that time. If I remember correctly, you don't go through passport control if you are connecting to another flight in Frankfurt.

They have sort of an odd system at the gates there. They don't let people into the boarding area until the desk is manned to check people in for the flights. Then everyone lines up and shows their tickets to be let into the waiting area when they open the gate.

Now that I think of it, I do believe that I got my seat assignment on the boarding pass I was given in Boston for the second leg of the flight.