Is it "holes in one" or "hole in ones" when someone gets more than one in a lifetime, say?

Holes in one.

I’m a golf fan so I felt compelled to seek out an answer. Dictionary.com says:

hole in one
n. pl. holes in one
The driving of a golf ball from the tee into the hole in a single stroke.

Similar to Attorneys-at-law. sons-in-law, secretaries general.

Ladies in waiting, matters of fact, powers of attorney.

But we do no longer answer “Is that your coat?” with “No, it’s somebody’s else.”

Holes in one. It’s just like I say I have ‘sons-in-law’ not ‘son-in-laws.

@gailcalled Excellent! As well, there are a number of animals that have the same singular and plural form:
bison – bison
deer – deer
moose – moose
sheep – sheep
swine – swine

Just saying.

Fish gotta swim…elk gotta run..