How Many Moves Deep into Opening Variations Do You Study?

I know some opening lines very deep.

However, I did not plan on that happening it sort of just happened.

Through study, repetion of games played, and chess understanding you can start to memorize opening lines with out even trying too.

I have memorized moves 25 moves deep in some variations of the Caro-Kann and Sicilian simply because I have played them so much. After a while if you consistancy try and improve and study you will begin to memorize the moves.

Now whether or not you willl be able to remember them and/or not forget them in another matter lol. However, It is very much possible.

At the same token I may only know some side lines 5 moves deep.

I have come to accept the fact. Their is no way to memorize every single main line, side line, off beat line, unsound line in chess.

One day you will run into an opponent who plays something you do not know. When that day comes you will just have to improvise.

I really do not have any ambition into memorizing 25 moves of an off beat side lines my opponent plays!

Frankly, I don't care if they play an off beat line if they win than so be it if they don't than. Obviously it was because my improvision was better than their line.

I doubt that, but thank you.  I play for the fun, adventure, seeing old friends, making new friends, seeing new places.

You've got it all wrong.  It should have nothing to do with statistical data.  It also should have nothing to do with how many moves deep.  Like others said, some lines may be 8 (Sokolsky), some may be 30 (Kings Indian Mar Del Plata with 13.a4).

What matters is do you understand it?  The Kings Indian Four Pawns Attack occurs no where near 20 percent of the time, but it is vital to understand if you play the KID as Black!

If all you study is the Classical, Fianchetto, and Saemisch, you are doing yourself a disservice.  You will just assume the Kings indian is all about getting in e5 and then f5.

Do you "understand" why e5 is bad in the Averbakh?

Do you "understand" why f5 is bad in the Four Pawns or Gligoric but not the Mar Del Plata?

It is details like this, the d4-d5 advance being the green light to pushing f7-f5 while doing that with the White pawn still on d4 and the ability to still open the position with d4xe5 will get your head chopped off!

It is not about memorization!

It is not about statistics and frequency

It is about UNDERSTANDING the big picture and then once the middle game hits, which may be move 7 in one game and move 24 in another, if you UNDERSTAND the position, candidate moves should come to you naturally, and instead of spending your time finding moves, you are spending your time on calculation!

I think TF is right, as usual. What I try to do, though, is trying to get familiar, if only a bit, with anything I can encounter in the opening, including inusual things like Grob or Sokolsky.

I study openings far deeper than I can remember what I study. I want to know that my openings are deeply sound and that a solution exists to the opponents problems and that if I lose its my understanding nit the opening. Studying them until the depth that I confident in the struggle that results, even if not remembered exactly, helps understand the patterns. I try to remember the openings until the key points. For the rest I try to summarize in words the theme of the rest of the play. If I believe in the deep soundness of the opening, know it until the key (non-intuitive but critical) move and have a general idea of the theme of my play that follows, I find that I play confidently, which is all I can ask for.

When I thought that chess was a waste of time, I would only study enough to reach a playable middle game, about two moves.

Now I'm older and know that chess is a waste of time, I study more complex openings and studied past move 25 plus several that I think are good after that.  Even with all this studying, what I can remember at the board is closer to only 10.

For OTB chess I try to get my opponent out of their comfort zone as soon as possible – especially into my pet lines that I have analysed a lot and understand well. Some of that analysis (stored in ChessBase files) can go very deep - even to move 30 or beyond - but actual OTB games never get anywhere near that. Just as well, because I wouldn't be able to remember most of the analysis anyway. In CC and online games, on the other hand, where I can just look it up... well, that's a different matter

For me it depends on the opening. Some require way more theoretical knowledge than others. For example, In many Dragon lines (which I play as black) I know anywhere from ~15 to 25+ moves of theory. It is fairly similar for me in lines of the Mar del Plata KID, The Poisoned Pawn Najdorf, the Classical Caro-Kann with Qc7, the Marshall Gambit, the Taimanov, and others. In some other lines that aren’t so theoretical I know just some moves like the Ruy Exchange and the Alapin. In one Caro-Kann I analyzed here I can blitz out 19 moves without thinking and only then does the real game begin. On the other hand, I know almost no theory in the Pirc because I generally will just play a system, either the 150 Attack or quiet System with Nf3, h3, O-O, etc.

Wow.  I wonder if you are a typical USCF expert.

In that Sicilian Najdorf game I've posted so often on the forum, my prepared novelty came on move 28. When my opponent resigned (on move 32) we were still in my opening prep.

Wow.  When things get back to normal, you should go and play OTB again.

Meh... I'm in my 60s. My "great future" is mostly in the past.

Depends. On Frankenstein Dracula variation I go all the way to move 13 around.

On alekhines defense (4 pawns attack) I just go to move 6.

on birds opening I just don’t.

For the Sicilian, though... I normally play the Alapin but recently I wanted to play the open Sicilian more often. I used to play the Chinese dragon as black, and that’s it. I knew literally no theory

Meh!  Age is not a reason to quit chess!  Andres Hortillosa claims you can Improve Your Chess at Any Age!  I'm 2 days shy of being halfway between 40 and 50 and I'm going back when OTB play becomes available again!

Nah I used books for openings

I still play non-standard openings most of the time so there's that. But when I do study an opening I focus on the position rather than the number of moves. This is a time consuming way to study an opening because analyzing each position usually means taking the entire game into consideration... so it's quite the investment to make.