Porsche Museum in Stuttgart, Germany

Could you do it as a day trip from somewhere in Europe or are you coming from the United States?

What do you mean by "the area"? Europe? Stuttgart? ;-)
In my opinion, the Porsche museum is not the best automobile museum in Stuttgart; I found the Mercedes museum much more interesting. So if your husband is a car enthusiast, he should probably see both museums. There is also a lot more to see within a one hour radius, but without knowing your interests, it is hard to give a recommendation.

Maybe we will end our trip in Stuttgart and fly home from Frankfurt?

What did you visit within a hour of Stuttgart? We are interested in architecture, food, cars, culture, etc...

You'll get more feedback if you can provide more information regarding your trip. But the quick answer is: if Porsche is something he wants to do, and you don't frequently visit Stuttgart, you should do it.

I agree with Chris-S: Porsche's museum isn't the greatest museum, It's more like a super fancy showroom with lots and lots of Porsches. Think of it as the "church of Porsche." I also agree that the Mercedes Museum is much better. The focus is world history as influenced by the automobile and it's quite well done. It's important to note that the two museums have collaborated to offer a dual ticket.

If you really want a Porsche experience, I recommend you RENT a Porsche. This can be ordered online and picked up at the Porsche museum. There are options for a half day or full day or longer and it's absolutely worth the cost. They will even provide a suggested driving route, based on your interests (castles, countryside, autobahn etc.) I did this for my husband last year and I had three marriage proposals from complete strangers as we were picking up the car. =)

I think Stuttgart is a gritty, hardworking city but with a lot of hidden gems in terms of dining and experiences.
PM me if you'd like more details.

Also, you can fly from Stuttgart to Atlanta on Delta, so no need to drive back to Frankfurt.

You might want to check out Tübingen, Heidelberg, Ludwigsburg, or Schwäbisch Hall. The locals will probably be able to add more information.

Stuttgart may be hardworking, but it isn't gritty at all. This is a typical prejudice that even many Germans have who have never been there. In the city center and on the hills that surround the center you would never ever realize it is an industrial city. In fact it is one of the greenest cities in Germany with more than 50 percent of its area consisting of parks, forests, orchards and vineyards. The (rather clean) industries are all in the suburbs.
The construction site of the new Hauptbahnhof (main station) being part of the rail project Stuttgart 21 doesn't make the immediate surroundings of the station look nice, but you only see it when arriving or departing by train there.
For ideas what to do in Stuttgart and its region have a look at https://www.stuttgart-tourist.de/en

See if you can take the Porsche factory tour - so much more interesting than the museum. We had one full day in Stuttgart during the semi-finals of the World Cup in 2006, and Stuttgart amazing. I can't believe it was so long ago. The Mercedes museum was close by the Porsche factory.

demag, please excuse my use of the word 'gritty' as it was not intended to be an insult in any way. I am very fond of Stuttgart and find it's mix of industrial, urban, and tranquil green to be a wonderful combination.