how long are your variations?

I'm curious to know how many moves you're able to calculate.

I'm studying a book that analyses GM games, and trying to follow the lines in my head is a big effort (I need to improve on this).

Most lines of this book go at about 8 moves deep. (Of course for "move" I mean white move + black move = 1, just to clear this up). I struggle a bit, sometimes even with 6 moves.

Note however that these are all lines where the position is an absolute mess, not simple moves.

Also, the challenge is trying to SEE the position after the variation, and still having some fuel left in the tank to give a general intuitive evaluation.

How many moves ahead do you think a GM analyzes in an average middlegame position? Are 8 moves enough or not?

It really depends on how forcing a variation is.  If it's very forcing, you might be able to see 10 move ahead.  If it's not forcing, you probably can't see more than 2 or 3 with any confidence.

2-3 moves ahead should be enough in 80% of positions...

In Correspondence Chess: infinite moves

in normal time controls up to 6 - 7 ...

i think it is not important to calculate long variations, but to evaluate shorter variations correctly (not that I am able to do it). If you calculate, say, 5 moves ahead and you insight/intuition/inner voice tells you you have advantage, you don't have to calculate deeper. This is my way to play chess. Note just the connection "to play chess", because chess is still a game. It is not important to win every game, but to have fun in every game.

Don't study chess, there is about 95% chance you can't make living with it. Just play it for fun, don't care about the points and enjoy every single move ;)

Here's an example to show what I mean.

I have the above position in the book. It gives some lines, among which the one I posted in the diagram. I spend some time on it reading and studying it without moving the pieces on the board. Eventually I manage to calculate and see how the board will look like after all the moves, and I agree with the evaluation of the author.

I was happy. Other lines are more difficult though, so I can't always get it.

Anyway; would you be able to calculate the thing above in an OTB game?

No, I would have not found the knight move and would have lost.

No I wouldn't be able to calculate the line (8.Rc1 is quite hard to see on top of other things).

Not in an OTB game, because my mind wouldn't be able to fully see the lines behind the piece configuration under so much pressure, but if my life would depend on it, maybe with 3 days/move. 

It's just a possible line given by my book, it wasn't played. It explains the reason why black didn't play dxc4.

If anybody is interested, the game is this one:

http://www.chessgames.com/perl/chessgame?gid=1070847

The point of my question is for me to understand how my calculating power compares with you guys; having an idea of whether I'm doing good or if my calculation is a weakness.

Also I wanted to know if to become a 2000 rated player (my goal) one is required to see such lines.

From your posts you seem to be a strong player, may I ask you what your OTB rating is? Just genuinely out of curiosity.

For all the others who answered honestly: thank you, I really appreciate :)

I might post some other example line if I find a really cool one.

depens on the position, OTB i probably do about 4-5 moves which is easily enough imo.

I really don't think I'd be able to calculate that in an OTB game.

It varies.