approx 1 month...It all depends if you give into the whimpering. Once we determined Allie was whimpering to be let out, and not for a potty break, we started ignoring it specially when we took up the water at 8pm. Once you determine that its not a needed potty break, you can ignore it and over a week it should stop. BUT make sure its not a needed break. I did this by counting how long they pee'd. When she went for 8 seconds, it was needed, 3 seconds she was playing me... For a puppy under 6 months, I would do like 5 seconds, needed, 2 seconds, playing you to get out...
I think it really depends on the dog. Bailey started sleeping through the night 1 week or so after we brought her home. She's 15 weeks now, & when I get up early for work, she doesn't even want to get up & out of her kennel at that time.
Those times when they get up in the middle of the night feels like you have a newborn!!
Lexie was sleeping through the night at about 9 weeks. I would take her out @ 11:00ish and she would sleep until about 6:00 a.m. She's been really good about her crate at night. Monday and Tuesday nights were a bit rough; I couldn't get out to play with her as much as usual and boy did I see the difference in her sleeping. She was really unhappy and waking us up in the middle of the night. Yesterday we were back to our regular routine and she was fine at night again.