The brain needs rest to heal, just like any other injury. The brain needs extra downtime to recuperate and repair itself and rest is essential for neurogenesis and neuroplasticity to occur. If everyone's concussions healed within 1 day then nobody would have PCS and nobody would have long term lingering symptoms.

Sleep is important because the brain flushes out excess gunk while you sleep. If you are not getting enough sleep at night, then nap during the day. Also take mini-breaks throughout the day to allow the brain to recuperate.

There are many reasons why you would want to avoid extended rest but healing the brain takes priority so that's why I emphasize a gradual re-introduction of activity. Because you aren't going to go from a dark room to an all-day music festival right away. It can take days, weeks, or months, depending on your condition so I would avoid setting a time limit.

The most important thing is that you make steady improvements, even if they are small. If 1 day of rest is all you need, then great. But if your condition is not improving, or if it is getting worse, then you need to adjust your strategy and give your brain more rest.

People should not have to suffer with PCS symptoms for months after an injury. Most concussions heal within 7-10 days. When people have symptoms that last longer than that, it's probably because they didn't rest enough in the beginning.