The nightscape shot could be just sensor heat causing the noise, hard to tell
The fact that it was a 30 second exposure should certainly be taken into account
A lot of posters also seem to be talking about "prints". I think we need to appreciate this is the digital age, photos are photoshopped to death and used for various personal and commercial electronic output.
For many people:
It is of supreme relevance what photos look like SOOC and pushed.
It is of little relevance what photos look like in a print - I can't remember the last time I printed something, and the photos I have printed are just rolled up in my cupboard somewhere. Who has so much wall space to display all these prints?
And how many of the images that you post/share digitally are 100% crops? As a matter of fact, since digitally displayed images are lower res than what is needed for a good print and therefore down-sampled more, noise is even less relevant for them. It is the print makers, especially those making 12x18, 13x19, A3 or A3+ which are hand held and viewed close up, who need to worry most about noise.