I've done multiple 25 and 50 milers on my Dahon D7.
For me, it was comfortable right out of the box.
Come to think of it, the stock tire failed during one of the 50 milers! Had to repair it with a boot so I could continue! I replaced both tires with 1.75" Schwalbes.
I put another saddle on it that I thought would be more comfortable, but went back to the stock seat after a couple of rides.
Oh, I added Crane Creek bullhorns and clipless pedals.
Hmm. My position isn't getting any better here...
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Fewer Cars, more handlebars!