Most of the time an assignment is for 13 weeks, or 3 months. This is far and away the most common. Once in awhile a facility will have a short term need and put up a travel nursing job for 4 weeks and sometimes other terms but almost all of what you will see advertised are for 13 weeks.
Once that 13 weeks is up, though, if everyone is happy you may well get offered an extension. If they really want you the travel nursing agency you are working will likely offer you a bonus to “re-up.”
Always ask.
If you want some free information on travel nursing jobs click HERE.