It depends on what you mean by long-term and probably how well you take care of it. Growing up, I lived in one for years with no issues. So did my best friend, for even longer (at least a decade, no issues with sagging or warping). And this was in the rainy, wet Pacific Northwest.
I dare say they are better built than the flimsy plastic tent we saw linked in the OP.
Yes, you can spend a lot more on one and get nicer finishes, but the end state is the floor sags and none of the doors shut.