From what age could a Levite serve in the Beit Hamikdash (Temple)? And until what age?
AskTheRabbi.org answered:
The Talmud, Tarctate Chullin 24, teaches that the Levites began training to serve in the Temple when they were twenty five years old and they began their obligatory service when they turned thirty. A Levite could serve until age fifty.