In "advanced" you may not think you need repetitive practice. And it may be true if you know the theory fully (or choose to do your own version hoping to reread it one day).
Repetitive practice is good if
--you want to build speed. Going over the same item will help you gain that speed because you will have memorized the outlines. You will also begin to understand the theory and the "why" it is taught that way.
--you want to sustain speed. Once you have the outlines "memorized" and theory understood, you can keep your speed up. With theory you won't Wonder if you should add the letter 'a' to the first of a word, omitting the letter 't', etc., because it becomes second nature.
--you want to improve your shorthand vocabulary. When you need to learn a new outline, writing it over and over will help you know it.
--words you write today seem a bit hard. When you review and keep working on the basics of Gregg shorthand, you will see how they apply to the advanced shorthand you write. Those beginning vowel lessons, will help you with new words you encounter and write.
--you find reading other shorthand notes or books hard. Reading over and over, even the basics, will help you see how the shorthand works together as whole and future reading will be easy. If you plan to type up what you have written, you want to make sure you can read as well as write. Reading shorthand also helps with writing shorthand.