I'm a USCF Expert and don't think I know any lines after move 15 (that I play anyway). I find the best idea is to know the opening ideas and follow principles.
For awhile I was really worried about my repertoire and it took some of the fun out of chess for me.
I find it's best to just relax and have fun :) Yes, you do need to know some stuff, but as long as you're not losing because of bad opening play, forget about what some people write about learning 20+ moves of theory.
It seems nowadays to become a good player you need to have studied and memorized a good amount of opening moves and also various "trap lines" to avoid major blunders.
Some people on Chess.com talk about knowing 20+ moves deep into some openings and even into the middle games, in order to be well prepared.
Has this need for greater memorization and knowledge of opening theory taken away some of the joy or fun of chess for you guys?
Back in the old days, there was less rigid opening theory and knowledge and players could play not-so-great/bad openings and just fight it out in the middle game. But, now, it seems like you have to have these set lines 20 moves deep just to get to a middle game where there isn't established knowledge yet (or, at least, where it's not as clear what is a good/bad line or move).
Thoughts?