Until the cows come home is an idiom. We have all heard it, we have all used it or know someone who uses that phrase. I caught myself saying it to one of my customers. It means a very long time. But why? Why cows? Why not Sloths? Cows are notorious for taking their sweet old time to do things or to get from one point to another. "You can do that until the cows come home and never get anywhere."
The precise time and place of the coining of this colloquial phrase isn't known. It was certainly before 1829 since that is the year that the phrase appeared in print. Groucho Marx made the phrase famous in his movie Duck Soup in 1933.
At any rate, I will love you 'till the cows come home!