With the oil-based finishes, they are a two coat application from the get-go. (One coat is necessary for routine maintenance applications)
The water-based finishes are a stain application (one or two coats depending on the product), and will have a clear sealer coat applied over the stain for the final look. (One coat of the clear coat is necessary for routine maintenance applications)

Depending on the amount of sun your home is exposed to, the finish will last 3-6 years before maintenance coats are needed. If the home is highly exposed to the sun, (especially on the South & West sides), you can expect to reapply every 3-4 years. If the home is well shaded or protected by covered porch, then 5 or more years are the general life expectancy.

Read the each manufacturers application guides for their recommendations.