When I did my PhD there was another PhD student of Biology who lived for 3-4 months in the lab. That was in Central Europe btw. :) He had to move out of the dorm he lived in and then didn’t want to look for something new since rents were too high for his taste. After the aforementioned months the Prof told him to find somewhere to sleep than the labs cafeteria where we used to have a couch, so he found a new place eventually.