Since the longevity test inputs always very from person to person in order to better simulate that there will a lot of paramterization that needs to be done on your part. Its not hard but depending on how many questions you ask might take some time. If your test outputs a specific result, like how long my lifespan will be, you can try to extract that number. So in general it all depends on your tests and goals but there is nothing really special about the longevity test, it's just a giant form and bunch of user inputs that you'll need to work with but if my memory serves me well you shouldnt run into too much trouble since really you're dealing with 2 page transaction (the form and the result)
I am little confused by the question. Are you trying to execute a load test for longer than 24 hours? What seems to be stopping you? Setting a time or transaction limit places a hard stop on the test. Keeping the transaction limit to 0 will run the test indefinitely (stop test with user interaction).