Karp recently turned 90 but there was no conference to celebrate that. Which numbers do we use and why?

Karp turned 90 in January of 2025. I searched to see if there is a 90th Birthday Conference for him.  I did not find one (is there one?).  For which years do we have celebratory birthday conferences?

Here are some conferences in honor of  60th Birthdays, by alphabetical order of last name. 

Eric Allender here

Laci Babai here

Allan Borodin here

Rod Downey here

Juris Hartmanis (at the 1988 Structures, now Complexity, conference, predating the web). Lance posted about it here.

Russell Impagliazzo here

Richard Karp (I could not find the link.)

Stuart Kurtz here

Michael Rabin (I could not find the link but I recall planning to go but snow cancelled my flight.)

Michael Saks here

Alexander Shen here

Michael Sipser here

Shang-Hua Teng here

Leslie Valiant here (I thought he also had an 80th bday but I am wrong- he is younger than 80.) 

Vijay Vazarani here

Nikolay Vereschagin here

Avi Wigderson here

I am sure there are more. 

Having a conference for someone's 80th birthday is also done. Here are a few:

Richard Stanley here

Michael Rabin here

I am sure there are many more. 

Numbers between 60 and 80 are rare (my wife read this and noted that there are 18 of them not including endpoints) but here are some:

John Osborne  (UMCP Math Prof) had a 64th. Could not find a link. 

Harry Lewis had a 70th, see here (I asked WHY 70? He said the organizer, Margo Seltzer, wanted it then. That is another point- the organizer really controls which year and also if it happens at all.) 

Leonid Levin had a 75th, see here

Dick Lipton has a 75th, see here

Manuel Blum had a 77th since 77=7*11 is a Blum Integer. ( The only reason I know it exists is because Lance went to it.) 

I've seen 100th bday conferences. 

Turing here (This is one of many Turing Celebrations for his 100th. It was in 2012. Turing died in 1954.)

Erdos here (This was in 2012. Erdos died in 1996)

Chernoff here (He attended. He is still alive as of this writing, at the age of 101) 

Kolmogorov here (The Day K turned 100 a student told me this. I then gave a lecture on Kolm complexity instead of the planned topic, on the fly. Now that my course is all on slides, and some classrooms don't even have  a blackboard or whiteboard, I can't do that anymore. Oh well.)

I am sure there are more. 

1) Why are 60, 80, 100 the usual numbers? They are nice and round. And 60 is big enough so that the person being celebrated has done stuff, but not so big that they are dead. 

2) There should be more clever ones like Osborn (64) and Blum (77). If there was ever a conference in my honor that would be hard, since the number most associated to me is 5/12 (see here). I had not done much in math at the age of 5 months. Oh well.