I have heard you have to be careful not to overchurn when making homemade ice cream. But, the person telling me this could not explain. What happens if you do overchurn? …and, how do you know when enough is enough? 
This says the ice cream will get an icy texture.
Yep. Ice cream isn’t something you can just walk away from and come back whenever you feel like it. You have to keep an eye on the consistency.
Unnecessary precautionary warning.
If you’re talking about a manually cranked churn, most of us mortals can’t overchurn it because it gets thicker and more and more resistant, which is not only how you know it’s time to stop churning and let it solidify, it’s also a self-limiting endeavor. You go from one-handed effortless churning to needing the second hand to stabilize the churn as you go UHHH and yank and crank with considerable effort to make the thing rotate, and if for some unexplained reason you didn’t take the hint, it would get to the point that you would need a companion to hold the churn with both hands while you grabbed the crank handle with your own two and tried to make it move.
An electrical churn is also inherently self-limiting: it cuts off when the resistance gets high enough.
Moved to Cafe Society.
Colibri
General Questions Moderator