Technically, SAT scores never expire.
You definitely shouldn’t worry about the validity of your scores if you take the test your junior year and want to use those scores to apply to college.
Certain institutions place restrictions on the length of time between taking the test and submitting an application, but it’s usually around five years. We cover this in our How To Get Into The Ivy League series, which I recommend reading if you are interested in admission to an elite schools.
According to the College Board:
“Official score reports sent to colleges five or more years after a test date are accompanied by a message explaining that they may be less valid predictors of college academic performance than more recent scores.”