They say they can hold it for as many hours as they are months?

i got my cleo when she was 8 weeks, maybe 7 (she was adopted, so we can only guess her age) and yes, for the first week, i had to get up in the middle of the night to take her out... she would cry in her crate, and thats how i knew she needed to go.. but that only lasted about a week... which means she was not even 3 months before she started holding it all night, like, 7-9 hours sometimes... she's well housebroken for the most part, but did i just get lucky, or is every dog really different? she's a large breed, we think... at least a big medium, lol/... but i had a 7 month old 4 lb pomeranian and she also would hold it for 10 hours sometimes... out and about too, not forced to wait in a crate... so, just curious how well that staement really holds, or if its just a guideline for new owners