When does de opening end?

When does, practically, the opening end ?

As I can figuer, trying a few ones wih Penguin, it is around moves 5 to 8

Is that right?

At the beginning of the middle game! Seriously, there is no clear answer to your question as there is so much theory written and analysed about certain openings that it all depends on the type of opening and variation.As a general rule the opening ends when books switch off and you have to come up with your own plan and strategy.Hopefully this helps.   

Some games can stay in opening theory for 15-20 moves, mostly GM games though. People with lives want to get the opening over with and on to the good stuff.

I remember some author long ago saying the opening ends when the pieces were developed.

Theory may go on, but as counter-intuitive it seems to those of us who have studied lots of such deeply-delving lines, it may be middlegame theory that we are really looking at.

I don't know, I think that once you're out of the theoretical best moves for both sides then it's middlegame and before that it's opening. That's not to say that the first five moves played poorly don't constitute an opening of course.

For example if I play 22 moves of theory into the Ruy Lopez I consider that to be still in the opening.

Usually it's where you have to start thinking for yourself.

I agree with this particular version of Kupov, and by extension Spud. When the opening theory ends, so does the opening.

there's no set moment, obviously, but "when your rooks are connected" is a decent sign-post for a lot of openings.

Well, some opening variations have theory reaching well into the middlegame and even into the endgame. Other variations don't have theory beyond move 5 or 6 yet. It seems that the opening stage is roughly over when the minor pieces have moved at least once and the Rooks are connected.

You could have a knight laying dormant for 20 moves or more if there is a quick attack, or your bad bishop in the French might refuse to leave his spot until the mess is cleared toward the endgame. I don't think it makes sense to say that it should end by a certain move number, especially when it doesn't follow a standard by either definition. Nor can you say that it ends because it's the middlegame now, because that is precisely what we are trying to define...

I'd say it (when the pieces are developed) is a rule of thumb that doesn't need to be dogmatically applied to all instances yet still be valid.

Haha, dogmatically

In a previous life all my writing was spiced with Shakespearean puns. That's karma for you. Now we see the extent of my humor unleashed.

It is also possible that one side has entered the middlegame while the other side is still lagging in the opening. (If so, they might never make it out though.)

 What is a de opening?

Mr Cpawn

Excuse me, Mr Cpawn, that I might have unconsciously offended your literary vision by such a phonetic misspelling when I wrote "de" for "the".

Could you ascertain the "why" of the error? I bet you a couple of beers. . .

I love it!

When the development is completed or an attack has started

When you get off your own opening book. Theory may go on for 15, 20 moves but if you only know up to move 2, that's when the opening ends for you.