How long is a TOEFL score valid?

A TOEFL score is valid for only two years. 

After two years the score are usually deleted from the TOEFL database and will no longer be accessible by the student or by universities.

Even if you still have a copy of your original score the universities will only accept official scores sent directly from TOEFL.  Therefore, the TOEFL must be retaken after two years if you wish to submit your score.