Typically, most doctors will tell you that it is a lifelong condition influenced by genetics. They will also tell you that the best way to treat it is proper management.
When they refer to managing the seborrheic dermatitis, they typically imply one of three things: an anti-fungal solution, an antibiotic solution (if they are less familiar with seborrheic dermatitis), or a corticosteroid. These are all typically prescribed for a period of two weeks. But if the seborrheic dermatitis returns, then treatment is usually recommended on a long term basis.
Additionally, from my personal experience and from communication with others on the website, it appears that most medical professionals provide patients with very little information on seborrheic dermatitis. Plus, it seems that the recommended solution that the doctor will usually recommend depends on their own knowledge of the condition. The more up-to-date doctors seem to prescribe anti-fungals, while the less up-to-date simply go with a broad-spectrum antibiotic and corticosteroid cream.