
Have a ten year old who suffered retained testicles, he had other issues as well, so when prepped for an operation which x rays showed he didn't require asked that he was neutered rather than have to undergo another GA. It's dreadful but looking back can't remember exactly how old he was but around 12 months, whether in his case they'd never worked properly but I'd leave well alone for as long as possible, as Otto has remained a Puppy - a geriatric puppy & a silly little boy - we joke he's go a picture hidden somewhere & call him Dorian Gray.
Realise & agree with everyone they do need to be removed, but at eight weeks there's still plenty of time for them to appear.