I have an old gelding who's alone now. My property is just too small to support more than one horse. When I bought the house there were 4 other horses kept there with him (in a ~tiny~ round pen knee deep in their own mire) were taken away. I thought my gelding would become very unhappy, but he never neighed for them or acted lonely.
It's been almost 2 years now that he's been alone (without other grazing companions) BUT he does seem happy. I spend A LOT of time with him. When I don't work I spend about 4-5 hours a day with him, and the days that I work he gets about 2 hours with me. I groom him twice a day too because he loves it. We used to ride every day but he's been sick lately so now we go for walks together EVERY day - once a day if I'm working and twice a day if I'm home.
I have other animals too. I have 2 dogs, 3 cats, and 3 chickens too. He knows all of their names, and he seems to really like my chickens and my siberian husky. Oddly enough, the chickens and the husky seem to seek his companionship too. It seems mutual - especially the husky. The chickens want his feed but the husky just wants to anywhere he is.
The only thing that bothers me is that he has 1 spot on a hill where he likes to stand, sometimes for hours, like a sentinel. He doesn't stay there ALL the time, but he does go back to that spot when he's finished grazing for the time being etc. He'll stay there for hours, then graze, then walk around and nudge other animals... then go back to that spot on the hill and stand like a sentinel...
I do think he's happy. He eats very well. His eyes are bright. He whinneys and gets excited to see me. And he hangs out with the dog and the chickens a lot. But the hill/sentinel thing.... I just don't know what to think about that. Does anyone have any ideas?