We don't have a time limit. We can go months without ever being overcrowded. Near Christmas we're just about cleaned out. I can hold about 150 to 200. Sometimes we get litter after litter after litter when we're in the height of kitten season.
Dogs come in heat twice a year.
Cats come in heat according to the weather. I get hordes of kittens in May and June. I can get 70 or 80 a day for three weeks solid. I guarantee you I can't find homes for all of them. It happens again in October.