It depends on the horse- the ones I've seen that were gelded that late in life didnt really know anything different than to act like a stud.. I think the younger the better.
If he's hyper its probably because of the poor training he has got as a race horse-- he's been trained to run- not be a pleasureable riding animal-- gelding him will not fix his training flaws!
If he throws correctly put together foals with a good calm nature- id keep him a stud and market him that way. --my opinion.
He throws beautiful foals BUT there are so many thoroughbreds out there right now that I can't justify making more. Plus he was only raced to 5 years old and didn't have a chance to win much so no one in the race industry would look twice at him. We've put out adds to sell him over the last year and had no takers. My decision to geld him is mostly to make his life better. I hate seeing him alone in that pasture. He's been there for 10 years. I just didn't know if there was even the possibility of ever riding him.
Thanks for all the replies. I think I'll geld him for sure then take it from there. Worse case is he won't be rideable but will be able to be turned out with the geldings. Great advice to turn him out when he is still feeling a little "under the weather". I'll try that for sure.
Oh I also wanted to say that he is not aggressive. He is pretty well mannered for a stallion who is only handled a couple times a year. We had to move him to the barn yesterday to switch some mares around and he walked really good for hubby who had to walk him by a fence with 2 mares. He hollered but he didn't act up.