Little House on the Prairie first began airing in 1974. It continued to air regular episodes through March of 1983.
For season nine, the show transitioned to a new name Little House: A New Beginning, starting in September 1982. It continued under this name for only this single season.
Three television movies also aired following the end of season nine, which are sometimes referred to as season 10. These two hour long movies aired in December 1983, February 1984 and December 1984.
So officially, the run of Little House on the Prairie, including the concluding television movies, puts the show as running for ten years.