1.at 6 months-1yr.
2.after he passes puberty, say about 2.
3.after he reaches full maturity, anywhere from 3-5.
Personally, I think that for RESPONSIBLE Akita Owners, it should be done AFTER puberty(there ARE important hormones that those testicles supply!!!) and close to maturity. Age 3 at the earliest. Age 2 at the Absolute Earliest. All other dogs should be Tutored at the vet's earliest convenience.
Now, that said, there are lots of mitigating factors.
Is or will there be there an intact female canine within a mile of you?
Is he from an aggressive line. EARLY castration MAY prevent him from becoming as agressive especially IF you train him properly.
Are there any other medical issues with him? Anesthesia concerns?(if so, combine with another required operation)
Now, my favorite stat. PLEASE remember this if you dont remember anything else. If your canine reaches the age of 10, there is a 90% chance he will have serious(well, arent all problems back there serious?) testicular and/or prostate problems. Mostly cancer. Yes, it may kill him. BUT, If he is neutered, the chance is zero for testicle probs of course, and almost zero for the prostate. (stat info source: vet texts)