After some discussion and sending him the link he seems a bit happier, even referring some of his friends to us for a kitten out of a future litter. I found that the kittens recovered back to their normal behavior within 2 days of their spay and neuters. Hopefully he continues to be happy with them.
It sounds like you had the surgery and let them go to new homes right away; not a good idea. You should keep them for over a week, particularly girls, to make sure there are no complications that need to get attention and to avoid stresses being so close together. Issues of infection and anaesthesia and even bleeding can takes days to appear.
We did keep those two for a week after surgery, 2 others for 2 weeks, and the last one for 3 weeks. He basically sent an email the morning of pick up saying he was flying his plane over to get them. It was all very short notice, and we had originally told him when they would be ready to go, which was a week later the pick up. I now know for the future not to let anyone say they are coming to pick up a kitten before the date they were told the kitten woulld e ready to go home.
Aha. I thought you meant you "found that the kittens recovered back to their normal behavior within 2 days of their spay and neuters" from the new owner, but you meant that was what you discovered/observed yourself.
Kittens will act normally the DAY of surgery, even though you want them to take it easy. ; )