I stretched them to 2.1m. That was on the balcony, I had put a foil on it as a windbreak (one pole across the top and one underneath).
The pole is so stable that the upper one slipped down in strong winds, but that's because there's as much force on it as if you were hanging on to it.

In my case, the rod is set to 1.60 and makes a stable impression. Presumably the function is also guaranteed in the maximum indicated extension length under normal load.

I only stretch the pole to 1.50, but with a relatively thick curtain, serves as a divider in the hallway. It is very stable, but I cannot judge whether this would also be the case with 2.20, but I think so.