Most cats can stay for up to 8 hours in a cat carrier. It is generally advisable to take a break every two to three hours. There might be circumstances where you might have to keep your cat inside the cat carry box for a more extended period of time. During these times, ensure that your pet does not get stressed out with the journey. Pack enough food and toys to keep your little buddy entertained. Plan every little detail in advance to ensure that the journey is comfortable for your little buddy. It is also important to know that a cat can hold its pee for up to 24 hours; Some cats can even hold it for 48 hours without any problems. So, there are almost no chances of a trained cat ruining your family car trip with the pungent smell of its pee. No guarantees, though!