At the end/At the end of the lesson

[englishhobby]

I've always thought that we should say either "in the end" (without any other words after it), or "at the end of (some activity)".
Here's a context where "at the end" is used without any following words (though the activity is implied - at the end of the lesson). Is the last sentence below correct? Why not "in the end"? Would it change the meaning of the last sentence?

Also we’ll have conversations on a particular topic in small groups – obviously in Spanish! – And then we discuss it together at the end.

 

[Raymott]

There's nothing I know of to validate that there is choice between "in the end" or "at the end of something". Either 'in' or 'at' can occur in the short and long versions.
In this case, "at the end [of the lesson]" is natural. We don't say "in the end of the lesson."

 

[englishhobby]

Either 'in' or 'at' can occur in the short and long versions.

I can't think of any long version with "in the end (of something)". For me it's the same as "finally", so no other words follow this expression:

In the end they got married.

Could you give some examples with a longer version of "in the end (of something)"?

 

[Matthew Wai]

'They got married in the end of the long-drawn-out romantic relationship well-known to their kith and kin.'
Is it possible?

Not a teacher.

 

[Raymott]

"... in/at the end of Summer ..." It's true that 'at' is more common there. Physically, something can be "in the end of the pipe/hose, etc."

 

[Odessa Dawn]

Hi Ray;

Why did you start the word summer with a capital letter, please?

 

[Raymott]

No reason; I was tired.

 

[englishhobby]

'They got married in the end of the long-drawn-out romantic relationship well-known to their kith and kin.'
Is it possible?

Not a teacher.

I think it's still "at the end" (= at the end of a series of events).