When I was in Dharmshala India in 1986 I met a Tibetan Lama who was in retreat in the dark for 17 years

He was the one that the character Yoda was based upon. His Name was Lam Rim Geshe. He was one of the most amazing people I ever met. Even though he only spoke Tibetan I had a translator who was a  Tibetan Buddhist Monk with me at the time. He looked a little like Yoda but he was between 5 foot 11 and 6 feet tall and smiled a lot.

I have met other people who wanted to become Tibetan Monks but couldn't do the required 4 months in the dark in retreat to become a Tibetan Monk. One fellow I met was majorly freaked out by his 4 months in the dark. So, this isn't for everyone. The problem becomes what is your mind and your subconscious going to do when you isolate yourself in the dark for 4 days or 4 months. So, unless you are very holistic and comfortable with yourself and your mind to begin with this isn't going to work for you.

You have to be very centered in yourself to go 4 days without seeing the light or 4 months without light. it isn't for everyone.

However, I have done a Vision quest which is 4 days without ANY water or food of any kind and I found this helpful in understanding what a human being really is.

It taught me that we are much much more than most people realize but also at the same time much weaker and more vulnerable as humans than most people realize too.

So, it was helpful to me in seeing what a human being really is beyond any BS we try to make ourselves believe so we feel better.

Because Yes human beings are amazing but likely amazing in ways most people don't fully understand about themselves.

So, is it worth it to go without water or food for 4 days?

I think it depends upon the person.

is it worth it to go 4 days by putting yourself in a room in the dark.

Again it depends upon the person.

Is it useful to go 4 months in a darkened cave or room as a meditation?

Tibetan Buddhist Monks are required to do this in order to become a Tibetan Monk to begin with.

They don't cut their hair or fingernails for 4 months and one monk showed me his hair and his fingernails he had saved as a momento of becoming a monk in a 4 month retreat in the dark.

However, I think most Americans or Europeans might go temporarily or permanently insane going 4 months straight in the dark. It's not for everyone.

It might be useful to some people but not all people. It's a very individual thing.

By God's Grace