Yes, YEARS is a Scrabble word!

Letter values in Scrabble US: Y 4, E 1, A 1, R 1, S 1.

Is it a valid word?

YEARS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a late time of life
a prolonged period of time
the time during which someone's life continues
a period of time containing 365 (or 366) days
a period of time occupying a regular part of a calendar year that is used for some particular activity
the period of time that it takes for a planet (as, e.g., Earth or Mars) to make a complete revolution around the sun
a body of students who graduate together

Also: old age, long time.

Not playable in Scrabble US: GEEZERHOOD, YR.