Originally Posted by Faceman
The 60 day rule of thumb is based upon the half-life of testosterone and the time it takes for it to fall to an insignificant level, and is generally reliable to gauge when behavior directly induced by testosterone stops. However some geldings never lose some of their stallion behaviors, although they usually don't try to breed (although some do). Much depends upon the age they are gelded, and what their environment was - in other words have they been in a herd situation, have they bred mares, etc...
This. There are so many variables that come into play. We've always done ours as yearlings in the early spring before flies are a concern.
The only one that was done later is Woodstock who was recently cut at 5. He did still think he was big man for a bit but after a week with my boss mare who is sterile and wouldn't take his grief he has changed his tune significantly. Though with a less dominant band of mares I'm certain he would try to be top dog. His previous environmental factors were less than ideal though - first 3 years of his life were spent in a stall with no interaction with other horses or people, he hadn't seen grass even. When I first got him he was a rank *insert choice language here* We worked through all of that only to deal with an injury that held back training so he got the snip.