壽終正寢

1. • to die of old age
2. • to die in one's bed at a ripe old age
3. • (of a structure or machine etc) to come to the end of its life

     fig.

Character by character

• 壽(shòu)surname Shou
• 終(zhōng)end
• 正(zhèng)straight
• 寢(qǐn)lie down to sleep or rest