I normally memorise each measure, or section, as I learn it.
TAB is a wonderful tool for conveying ideas, but it can quickly and easily become a crutch/habit that is hard to break.
I refuse to believe there is limit to how much one can retain. The only limit is the speed with which it is acquired, and this can increase substantially over time as one learns how they best learn.
To a point Mark is correct about it being muscle memory…but I disagree when it comes to arrangements of slightly differing breaks and backups…these you have to remember if you wish to keep an order you’ve worked out.
Speed comes from familiarity and relaxation. Relaxation comes from familiarity.
To expand on the “toolbox” concept:
When you first begin playing music each note/measure is like a hill on a battlefield that must be climbed and flagged. As you fight your way up, it consumes all your attention, so you can’t make plans for the next hill until you win your way up the first.
As you advance, you can work on drawing a map of the entire battlefield (break/song/section) and creating strategies (different combinations) for the next battle, while fighting on that one hill, because you’re already familiar enough with each hill that you don’t have to see it each time you need to recall it.
So while a beginner may struggle to get through a single note or measure, a more advanced player has played that enough times so they can just plan to play it in the next measure or two, because it has become less of a burden to recall, due to their familiarity with it…hope this makes sense…