Certainly not done anything like those sorts of distances on the Brompton.
Last year I did the virtual Brompton World Cup and did a 19 mile ride. Should have done the longer one really.
The year before I did a 27 mile ride on mine. But that took forever. I thought I was being smart by staying off the roads and following a canal path. It was fine at first while it was paved. And even the gravel sections were ok, but slower.
But as soon as I hit the unpaved, un-gravelled section it was awful. Very slow, very uncomfortable and just not enjoyable. The wheels are too small to copy with ruts and tree roots, and the tyres aren't as wide as MTB tyres to provide any suspension or real grip.