How long do you leave an ankle sprain in a soft cast?

As long as: Your doc states. (which is usually 1-2 weeks). A new one may be applied after that but anymore that two weeks in a soft cast and that foot is going to stink.

Time may vary.: May be changed weekly for a few weeks depending on the severity of the injury.

Not long: Most ankle sprains can actually be well treated in a removable velcro splint, or, alternatively, a walking boot for severe sprains, so that you can completely avoid any kind of cast. Every patient and injury is different, but the general rule is that once your symptoms improve, you can wean to regular shoes. Talk to your doctor about your options.