Depends what you're doing mate.
The vital parts of optimised recovery are what you eat after training and getting enough rest.
Endurance is low-intensity by default, so it gives the person the impression that you can go and go and go with no consequences. This is because it's using fat as a primary fuel source, and the body has that in abundance, even somebody who looks shredded can have 40,000 calories of stored fat no problem.
You'll see folk on here laughing at footballers for what's commonly referred to as 'burnout', and it's usually with younger footballers. It's a dangerous thing and can lead to loads of injuries further down the line, look at Michael Owen for a prime example. When you burnout, you can't just go and sit on the sofa for 3 days and chill and things will be fine again, it could be 6 months before your muscles have made a full recovery.
Humans are no different to animals, look at a sirloin steak. If you get a fresh one and hit it with a hammer, pull it apart and move it, it will respond as it is part of a healthy muscle. Cook that steak 'well done' (exactly the same as overtraining a muscle) and how does it respond then? It doesn't it just rips, or cracks if it's burnt to a crisp, or stays as one useless slab of hard meat, good for nothing.
If your body is fatigued and your mind is beginning to slow, it's telling you that you need to slow down, replenish it's fuel stores and focus on your mind. Without artificial intervention (steroids) you're good for nothing if you push your body past it's limits.
If I was you personally, I'd probably give it a lot longer than 3-4 days.
