This may not be entirely helpful, but there is another way to remove people from your landscapes (Hopefully this will work in photoshop).
For part of a short film I needed to remove all of the people from an outdoor scene. The amount of people and the complexity of the lighting made it impossible to use masks, so this is how I did it instead:
After setting up the shot, I recorded it for about 15 minutes. After capturing to Final Cut Pro, I separated the 15minute shot into three 5 minute segments, sped each one up by 300%, then overlayed them using the "difference" blend mode. This pretty much removed the people from the scene, leaving only a few tell-tale blurs which were negligible.
I'm not sure if you might be able to do something like this with stills, though.. What I'm getting at is that maybe if you took 3 or more 30second+ exposures and blended them together, you might have better results then with just one exposure.