I haven't retired yet, but the conversation came up in September of 2021.
Lunch with 2 partners, they wanted to discuss all of the wonderful opportunities that were coming down the line. "Guys, I'm not really looking for more responsibility." "I'm actually thinking of scaling back."
"When you plan to retire?" asked one.
I looked over to the other, who is more senior, and asked "when are we going public?" He kinda scoffed and asked how many shares I had. His demeanor changed when I told him. The paradigm shifted from them to me.
I guess the answer to your question really depends on the relationship you have with your boss, or clients that you might serve, and how YOU want to deal with it. Also, how much leverage you have to dictate the terms of your exit.
I intend to ask how much time they need from me once I've made the final decision that I'm going to retire, and will work with the company for a situation that works for everyone. Could be 2 weeks (I doubt it), could be up to a year (doubt that too).
Now, if your boss has no idea, you might want to let him know on a Tuesday, or Wednesday. Nobody likes bad news on a Monday, Thursday or Friday.