About 10+/- years when it was very low for a long time, some kayak acquaintences loved it because it gave them lots of free camping on the shore line and opened up a lot of nooks and cranies normally covered with water.
That would be from about
1995-2006, I remember it well. Never stopped me from going though, just have to modify your itinerary for the water level at the time.
Didn't mean to put a damper on Lake Amistad levels, I currently have a trip planned for October, just don't know yet what it will entail.