You can buy the practice exams as many times as you want - as Tug indicated that the questions are taken from the official pool I am wondering if the practice questions are chosen randomly. If not somebody could theoretically buy the package many times and basically would have bought the exam..? Therefore I think the practice questions are locked to a specific pool out of the official pool if that makes sense.
Regarding your pearson vue question; you buy the practice exam, schedule a time period when you take it and afterwards its gone. You don't have the chance to repeat (the same questions) over and over again, as the practice exam exists in order to check your knowledge but not to learn the questions and answers by heart.
