It is not advised to spend much time memorizing old NBME questions, especially since the exam is changing. Spend your time, above anything else,
mastering the content and you won't have to memorize old questions to get the new questions correct. If you truly understand the material, you will be able to manipulate the concepts as they are presented to you so you can use reason to derive the correct answer organically. Regardless of whether or not the old questions show up on the real deal, to study old NBMEs is not great use of your time outside of reviewing the exam when you complete it (this is an understandable time to review the questions). To screenshot every question and spend time researching their answers and reviewing them? Not worth it, at all.
Take everything (especially advice) you read on the internet with a grain of salt and try to read as many USMLE experience write-ups as you can. Sounds like
@malin did quite well, and his method worked for him, but one person's thoughts on the matter is not enough to devise a concrete understanding of what needs to be done to score high. Everyone has their own unique path, and you have to find yours.
To reiterate: this is just my opinion, so you should take what I say with a grain of salt, as well.
260+ on every NBME. Taking the real exam Sunday.