I'm not the person you replied to, but I can share my experience.

I used to drink at least 2 cups of coffee a day, and at least 3-4 of black tea.

over a year I slowly backed down to just a single coffee coffee in the morning.. then eventually switched to decafe coffee for that one. I had headaches for about a week, and I think I was irritable.

Recently I stopped even the decafe coffee, and now drink 1 or 2 decafe tea a day when it's cold.

I feel great, save money and don't miss the ups and downs of real coffee - I used to get the sweats, shakes, funny shallow breathing, etc. etc.

I also had no idea I was living life through a "fog", that I didn't even know about until a few months after I stopped. Life is much better now.

Literally just a few days of headache/foggy brain.

Then it‘s magically gone.

Not even close to a full week.

Just do it.

It was not bad. I wrote about it in the linked blog piece.

I also recommend /r/decaf where you can get support from others who have been and are going through decaffeinating.