User blog comment:Astrotorical/Blog of News: The Game... some more/@comment-422690-20120325174158/@comment-422690-20120326012725

If mana cards were discarded every time you used them, you'd need a massive amount of mana cards, something like 100 - 150 per deck. That's what I mean by deck size; it would be too large. A token-based system works best with destroying mana, since it's a globally collected resource.