OnCollisionStay stops firing after a second or two?

I just have a simple test scene with a Rigidbody box on a BoxCollider floor. Not even a mesh. But the OnCollisionStay message seems to only fire for a second or two and then it stops. What’s the deal here?

http://unity3d.com/support/documentation/Components/RigidbodySleeping.html

If your rigid body stops moving it falls asleep. Try adding this script to the GameObject with the RigidBody to test if this is your issue:

using UnityEngine;
using System.Collections;

/// <summary>
///	A simple script to keep a Rigidbody alive. This simply adds an
///	extremely small value to this transform's local X rotation.
///		    
/// Use this for testing triggers with stationary colliders
/// </summary>
public class StayAwake : MonoBehaviour 
{
	/// <summary>
	///		Runs on frame update
	/// </summary>	
	private void Update() 
	{
        transform.Rotate(Time.time * 0.00000001f, 0, 0);
	}

}