The honest answer for most students is four to six full-length timed tests, spread across the study window, with each one reviewed for longer than it took to sit.
That last clause is the part that gets skipped, and it is where nearly all the value is.
Why more is not better
A practice test does two things. It measures you, and it exposes specific gaps. Only the second one improves your score, and it only does so if you act on it.
A student who sits eight tests and reviews none of them has spent about twenty-four hours to learn one thing: their approximate score. A student who sits three and reviews each thoroughly has spent less time and has a list of fixable weaknesses.
How to review one properly
Budget more time than the test took. For every question you got wrong, write down which of these it was:
- Content. You did not know the rule or the method. This is the good kind, because it is a specific thing to go and learn.
- Careless. You knew it and misread, mis-clicked, or solved for the wrong variable. Look for the pattern: most students have one or two recurring careless modes, not random noise.
- Pace. You would have got it with another thirty seconds. This is a pacing problem, not a content problem, and studying content will not fix it.
- Guess. You had no route in. Note whether it was a topic you have simply never covered.
Then also review the questions you got right but were unsure of. Those are the ones about to become wrong answers on a worse day.
A sensible spacing
- One at the start, before you study anything, as a baseline. Studying before you know where you stand is guessing.
- One every two to three weeks through the middle of your preparation, each followed by a week of work aimed at whatever it exposed.
- One about ten days out, under full conditions and at the real time of day.
- None in the final week. Light review and sleep beat a fifth test, reliably.
Conditions matter more than people expect
A test taken in three sittings with your phone next to you measures something, but not the thing you need measured. Stamina is a real component of the score, and it is the component practice tests are uniquely able to train.
Sit them timed, in one go, at roughly the hour you will actually test, with the break where the real break is.
The one exception
If your score is being held back by pacing rather than content, more full-length practice genuinely does help, because pacing is trained by repetition under time pressure and by very little else. Even then, review each one: the pattern of where you run out of time is the thing worth knowing.