I was pushed pretty hard to neuter Frag by the vet. I knew to wait, and wouldn't have had a problem keeping him intact for life... he never had any problems associated with the balls, really. Vet thought it may help his weird aggression... I can't say for sure if it was what helped or not. The timeline is getting fuzzier for me, but he was about 2 when neutered, so finally maturing, and we were doing behavior mod like crazy for the human aggression, plus TONS of regular training and lots of confidence building sports like agility and dock diving.
Who knows if the lack of testosterone helped, or if it was all the behavior mod/training, or just growing up. May be a little of each. He's healthy now (with good hips!) and non-aggressive, so I can't say I would change a thing to find out otherwise...
Recon was neutered because he was cryptorchid and the breeder required it by 18 mos. I probably could have talked her into letting me keep him intact, as he was better behaved as an adult with the testosterone than he is now (ok he was a little humpy and sniffy but that could be due to lack of training on my part) and I liked it/he performed well, but with the crypt I didn't want to cause any medical issues, and he was full grown with (assumed) growth plates closed.
Patton will likely be staying intact for most of his life, unless something comes up. I've really liked all my boys with their bits. Haven't had any real trouble related to it. The age thing and medical issues does worry me, and based on studies it seems like the golden window would be a healthy mature adult neuter vs. staying intact indefinitely... So I may neuter Patton much older, who knows.