[HR] Question - Do "Buy Horse" Options Change?

For a few in-game days now, I've had my Sim call the Ranch Animal Exchange with the intention to buy a Horse. I'm not happy with the selection I've been offered, but it's been the same 12 Horses in the list every time. Do they ever change and, if if so, how often and when? I could add a Horse in CAS, I know, but I've done that every time so far and I'd like this Sim to actually buy one instead. I was hoping the selection would shuffle more frequently but, so far, it hasn't shuffled at all and it's getting annoying.

Edit: It did finally change. I'm not sure the particulars, but I last checked on a Saturday, checked again the following Tuesday and it was a different batch of Horses. It's just a guess at this point, but I'm suspecting it changes weekly, either on Sunday or Monday. Not enough data yet on this to be certain. Hopefully I get one soon with the traits I want. I only really like 3 in the first place.