For a data point, I'm a 6', 120-110kg rider with a FTP right around 300w, and I ride an older Dahon Mariner D7 without problems.

I don't post big mileage numbers on it, but I do ride it commonly for 3-5mile one way jaunts, often with a few extra kg stuffed in a Xootr Crossrack/Crossbag combo.

Like Shumaker said upthread, I also believe that riding style can be key to getting the most out of folders. I also avoid dropping off curbs-- although I do periodically-- and also try to avoid hard sprints where I might really be reefing on the bars. I don't bomb rough patches on the roadway, preferrring to take the smoother lines when possible, but the stock Kenda 1.5 (Kwests?) aren't averse to exploring urban dirt paths along the river.

I also stay up on maintenance, keeping things properly adjusted and lubed...and clean. I'm shocked to see what pitiful repair many leave their bikes in, and that can't help durability.

So take my case for what you will; maybe it sounds like a boring way to ride, but truth is I enjoy my Dahon quite a bit, and it even inspired me to get a 20" wheeled minivelo, which may, BTW, be another option for the OP to consider.