Hi MSGmat1,
With each new edition of the Official Guide, approximately 10% - 15% of the questions are 'replaced'; the OG13 and GMAT2015 were the exact same book, so there have been 4 'new' books released since then (one per year, including the GMAT2019). By extension, many of the practice questions that appeared in the OG13 have been cycled out over the years, but that doesn't make those questions less meaningful. In simple terms, new content helps to sell the new books.
In one of your prior posts (here:
https://gmatclub.com/forum/confused-whe ... l#p2082423), we discussed how using a 'book heavy' study plan might limit your improvement. Since it's been about 1 month since then, I'd like to know more about how you've been studying during that time:
1) What study materials have you used during that time?
2) How have you scored on EACH of your CATs (including the Quant and Verbal Scaled Scores for EACH)?
GMAT assassins aren't born, they're made,
Rich