This is the hard part about all this. You're never going to find a real black-and-white definitive answer. Every body is different. Every brain is different. Everyone is going to react differently to different things.
Is there a specific time? You're never going to come up with that. No one is going to agree with that. However, common sense says that if you continually bash your truck, down the road something is going to give.
We have to start moving on with a lot more common sense, as opposed to the numbers here or the days there. We know what's right. We know in our heart what's right. Let's move forward. If you choose not to, that's your choice, but let's lay it out and inform people as much as possible about what the options are for them and why.