Is it THAT much important to use premium sleeves?
I use simple sleeves and have no problems whatsoever. They fit better even. Also, the unused character cards fit back to the Hero boxes sleeved without problem but I think that sleeving them with premiums will make the box fatter and you may have a problem fitting them back together as you unlock boxes and sleeve new character decks.
Thanks! As a sidenote, I have already bought premium sleeves so for me there's no going back