Here's a serious answer to your question from my Sifu. 4:11 is where he starts to get into about how low and how longIt would also matter how deep it is of course but assuming it is a "good" horse stance. How long should I be able to keep it without stopping?
Everyone one is going to have their own take about the horse stance. You won't find much agreement about how long one should hold the horse stance.
This one is important in my training. A stance doesn't help if you can't fire the guns while in the stance.How long not important. How well you can kick out of that stance is.