I have been a "temporary" hire at the USDA Forest Service since 1997 (18 years). My supervisor would love to hire me "permanently" so I can have full benefits and job security, however the hiring practices for the Federal government, and for USDA Forest Service in particular, are horrendously unfair in the name of being uniform and unbiased.
I would advise anyone interested in a job with the Federal government to take a permanent job, but the temporary jobs absolutely do NOT lead to a permanent job. They really don't. Instead, take the permanent job in the outer reaches of society, and then apply for the permanent job in the place you want to end up once you are in the system.
The USDA Forest Service, at least, hires in two ways: they advertise in-house, and they advertise nationwide. Supervisors who are hiring must select either from the in-house list, which is all of the current permanents, or must select from the nationwide list. However, if they select from the nationwide list they must first offer the job to military veterans even if they barely qualify for the job. Staff officers of the hiring supervisors also get a good rating on their job performance if they hire minorities, so some will look at ethnic-sounding last names (because it's illegal to ask someone if they are a minority). But if the hiring supervisor doesn't want a barely qualified veteran, or pressure to hire someone based on their last name, they go to the in-house list of job candidates. This is why most of the jobs in more popular locations go to those who already have a permanent job within the Forest Service. They can actually review applicants credentials, interview several people, and hire who they'd like to hire if they do it from the in-house list.
If you already have a family, mortgage and husband's job to consider, then you're out of luck... but if you're mobile, the method above could work.