I rescued Bernie, a 9 year old male AG CAG about 5 weeks ago and for sentimental reasons, tried to change his name.
After three days, I tried a "Hello Bernie", he perked up and started talking after three days of silence.
Now every morning first phrase from him is "Hello Bernie".
The name I tried to change from Bernie is not important, but it is important to understand he responded to his original name very quickly while sitting like a bump on a log when I tried his new name for the first few days.