I always put a qualifier on the advice to do untimed vs timed practice. It's true that putting time pressure on yourself before you've mastered the concepts and gotten used to GMAT question types doesn't make sense.
But at the same time, don't ignore the methods for saving time. I don't run across many people who have endless time to study for the GMAT. So keeping your prep as efficient as possible is critical to maximising your score.
So that means while you're doing untimed practice, notice shortcuts in solutions that cut the time to solve a questions (things like estimation when the answer choices are far apart OR eliminating answers to narrow your focus). That's basically "squeezing the maximum juice" out of each question that you practice -- the best way to respect the precious time you have to maximise your score on the GMAT.