Short-term travel rehab and therapy jobs normally last 13 weeks, but some hospitals and skilled nursing facilities prefer to have longer contracts for their travelers like 26 weeks. But overall the length of the time can vary, but what is most important is that you as a travel therapist know what you want.
Are you looking for a series of short-term travel assignments all across the country that let you see and experience a bunch of new places or are you looking for a travel therapy job that is more stable and lets you stay close to your family and home.
If it is your first travel therapy assignment you may want to keep it short with an option to extend, especially if you are going to be working away from home. On the other hand if you are working close to home there is nothing stopping you from working a longer contract or extending multiple times. Whatever you decide is going to be best for your travel rehab career, make sure you let your recruiter know up front so they can work to find you the assignment that is the best fit for you.