At what age do the testicles fully descend into the scrotum? should pediatrician check the position of the testicles at yearly check up?

Yr at latest: The testis are usually down at birth but in some may be delayed. Six months is when I expect late comers to be down, if not by a year I refer them for evaluation. Once they are down they may or may not be evaluated at every checkup. When they approach puberty it is often checked to document proper changes & as part of teaching the kid to do self exams.

By 6 months: With a few exceptions, spontaneous descent of testicles occurs by 6 months of postnatal age. And the longer testis allowed to stay in warm environment, the higher degree of compromise of spermatogenesis from affected testis. Therefore, it became a standard practice to perform an orchidopexy (surgical procedure to bring testis into scrotal sac) before 1 year of age.