I was always under the impression that it is better to spread it out.
Oh definitely.
Often, not being religious about the time helps, if you are around at other times *not* feeding them. (If you are only at the barn to feed them, then varying feeding times really does no good, as they know that Mom Showing Up Equals Mealtime). But this is no guarantee, it depends on your horses.
Speaking of which, another thing that might help you would be to streamline the haying process as much as possible, so there is less delay in which they can get all wound up and start pawing. So, like, if you are going to have to get hay down from the loft, or open a bale, or weigh out the feeding (I know most people don't, but I weigh out my hay), do it right after you hay them so it is sitting there READY for the next time -- next time you just nip into the barn, grab the hay, and bang you're out there putting it down for the horses.
Training (that is, not rewarding undesirable behavior) really DOES work for this, though. Come visit sometime and watch my three guys, all of whom came to me as bad mealtime pawers, just stand there and wait politely
Pat