Inherently, no - time will not cause noise. You may have inadvertently damaged your sensor somehow if you tried to clean it manually or change a focusing screen or something internal with your camera.

I also doubt the ambient temp has risen enough to account for the difference, unless you were taking pictures in Alaska and you're now in a desert. But temperature will effect noise (you see this in astrophotography - but we're taking super long, repeated exposures, and even then its barely, if at all noticeable until we start messing with the picture in post).

Dust shouldn't show up as multi colored dots, so that's probably out.

My guess is that its you're photos last night were underexposed and they've been pushed too far in post and you're starting to see some noise.

Try posting examples and you'll get much more definitive answers.

Edit: OOOOooooOOOOO (after looking at your sample you've just posted) - thermal noise on the sensor from a long exposure. Is your camera's long exposure noise reduction feature turned on? That will help if its not on.