Expire them by time, refresh them by range (can see as they move). Constantly replan and I bet you'd get something reasonable looking, but _only_ if you add an obstacle that represents only what the creature can see. If you add the whole obstacle (regardless of what it can see), it'll just do the optimal thing, which is fine but may not "look right". So clip visibility with obstacle, add that, and union it with all known obstacles, then replan. Keep it fast by doing a union "in place" with known obstacles so your obstacle list doesn't grow unbounded.

You can imagine it would walk toward the goal until it sees a wall, then it would go either left or right for a step, then back for two steps, then left for 4 steps, then back for 8 ... because the A* "frontier" keeps expanding so it keeps searching along that frontier.

And if you're lucky, you just discovered the optimal search variant of the "Drunkards walk" search problem.