Lucky had 2 undecended testicles. I kept waiting for them to drop and they never did.
Sandy's info above also corresponds with what I was told - they usually drop very young, but can drop later.
Lucky had both of his removed at about a year (I read the cancer risk is 13x as great if they are not removed ... can't recall where I read that though).
In any case, Lucky had the surgery to remove them and the incisions were much bigger and the recovery time a bit longer. But he came through it just fine and I'm sure your little guy will to if his doens't drop.
(a.k.a. Lucky's & Sparky's mom!)