Relatively permanent... since the welfare reforms of 1996, you can collect a maximum of 5 years. That's why it's called Temporary Assistance for Needy Families, (TANF).
Used to be called Aid to Families with Dependent Children (AFDC), and you could collect it forever.
Under the old AFDC, the Feds designed the aid programs, determined eligibillity rules, etc - the States just administered it.
Under the newer TANF system, the Fed gives the States block grants, and while they do set some parameters (like the 5-year limit, for example), the States design & administer their own programs.
So, while there was always some variation, one State to another - for the last 13 years, there's been a lot more difference between one State's programs and another's.
That's why, although you can be homeless & collect here, or in those other States I cited (ND, KY, NM, or WA), that doesn't necessarily mean you can in Cookie's State. Every State has its own system.