I have shorten down my herd and slowly continue to, so if you see a horse that you really like don't be afraid to make a reasonable offer.
Also when my horses are up for offers, that doesn't mean low-ball offers. I may not be on the game a lot of the time, but when I sell a horse I try to do my research on what is the right price for that horse. Yes I sometimes overprice, but I have my reasons