Yes, you heard it here first Lego Knights. The Merlok 2.0 game is still in it's early stages and it shouldn't take more than a few days (maybe as long as 2 weeks if you're a very casual gamer) to complete all of the areas that are currently available to explore. The chatter coming from the Lego Nexo Knights Google+ community (founded by Envill the Purple Knight) is that higher star levels don't affect gameplay at all.
When you compare a shield power at 0-stars and the same shield power at 5-stars, the damage, duration, and charge time don't seem to change. Personally, I suspected that the charge time would increase as you level up your shield power, but that does not appear to be true.
So, what does this mean? Scanning energy is your most limited resource. Concentrate on scanning all of the available shield powers just once. Get them all to 0-star and enjoy the game. Sit back and relax until Axl gets unlocked or until the next area gets unlocked (one of the mods at the Google+ community reports that Rockland may be released before the end of February). Grind for bits and armor components so that you can increase the power and armor of your favorite knight(s).
AFTER you have all of the shield powers at 0-stars, then you can start working on advancing your shield powers.
Disclaimer: Yes, I know there is a way to level up your skills to 5-stars in the same amount of time that it would take to get all of your skills to 0-stars, but there are also reports from a few gamers that feel the charge time for their high level powers takes too long and they cannot power up once by the time they get to the 3rd battle of each stage. Stay low, my friends. At least until we see higher damage/duration for high level shield powers.