I only wait 20 minutes.. But to be fair, Bella only has a mug and a half of lo-cal. I basically leave it as long as I can, I go move the electric fencing etc so its usually more like 30 minutes but 20 is my minimum
RIP Blossie - 1985 to 8/8/09 - "All horses deserve, at least once in their lives, to be loved by a little girl."
The racehorses where I worked came in from walk, usually still blowing a little and sweating, they were hosed down, scraped and covered and put back in their boxes with their feed. Probebly no more than 20mins after coming back in.
Personally I prefer to walk last mile home so the horse is not blowing and has cooled off. Brush off sweat marks, spong if unduly heavy. Rug and turnout. While they roll and have a drink I make up the feed. I never turnout after work immediately with feed otherwise I find the horse doesn't go off and have a drink because he is anticipating his feed.
To me the important factors are Horse is Cool, is not Blowing and has had a drink - once he's had the drink I'll feed.