Hi Guys, Marty's son here.
I'm a bit of a bike nut. There is a wide range in folding bikes depending on what you want to use them for and how much you want to spend.
At one extreme in compactness and quick fold is a Brompton. They fold to a very compact package in about 15 seconds and are a nice ride. They are all the rage for trips to work in London and other cities that mix bus, train, and bike to get to where you are going. They range in price from $600 to over $2000. They are little works of art. While people have ridden all over the world on Bromptons, they would not be my choice for big miles. I think of them as a little errand runner. You can check them out on the web. Trophy Bikes in Phili is a big dealer, and the guy Mike who owns the store is sort of the "Les at EQ" of folding bikes.
At the other end of the spectrum are Bike Fridays. While they do fold down a bit, they don't fold nearly as small as a brompton, nor do they fold as quickly. A Bike Friday is really a bike that you can disassemble into a suitcase. It takes me about 45 minutes to take apart or put together my Bike Friday. Now the advantage is that a Bike Friday is just as fast as any of my expensive full-sized bikes. It is a quality capable bike that happens to fit in a suitcase. I would not hesitate to ride a Bike Friday on a 200 mile day or on any ride I would take any of my other bikes. They also have fantastic customer service and a range of options. Call them up, and they can talk you through the options. I'd bet if a Brompton were a better bike for your mission, they would tell you that.
Now, as my dad, Marty, said he has a Dahon -- Boardwalk 8 speed I think. So, why is that? Well he didn't need an ultra quick or small fold like the Brompton or a "serious" bike like a Bike Friday, and the Dahon is just a serious value. I think it costs about $300 new, and they are, I think, the biggest seller of folding bikes.
Google Brompton, Dahon, Bike Friday, and you can get a ton of info. If you want to know more, google "folding bike forums" and you will find the equivalent chat group full of folding bike nuts.
Hope this helps. Joe