Orchidopexy is done in cases of undescended testes at the age of :
"Congenital undescended testis should be treated surgically no later than 9-15 months. Surgical correction at 6 months is appropriate". - Nelson.
Cryptorchidism :

An undescended testis (cryptorchid) is the most common disorder of sexual differentiation in boys.
At birth, approximately 4 - 5% of boys have an undescended testis.
The majority of undescended testes descend spontaneously during the first 3 months of life, and by 6 months the incidence decreases to 0.8%.
If the testis has not descended at 4 months, it will remain undescended.
Cryptorchidism is bilateral in 20% of cases.

Consequences of cryptorchidism :

Infertility.
Testicular malignancy → Most common seminoma.
Psychological effects of empty scrotum.
Torsion.
Associated hernia.
Neonate
1 – 2 years
5 years
Puberty