If you always use from the same location it really doesn't add much other than possible retroactive unlinkability if you move or notice you leaked your IP address. If you move to a new location and then the police show up at your neighbors house a month later, they might not be able to link the interesting session to you. If you notice you accidentally fucked up and leaked your IP address, you can stop using your neighbors WiFi and then when the police show up they might not be able to link the session to you. I think on a scale of 0-10, using WiFi from a neighbors house gives you +1 to anonymity, whereas using WiFi from random locations gives you probably +3.