Medium: The medium size is the most versatile & multipurpose since it can accommodate most holiday gift card sleeves as well as other common things
Once you've announced that you're casting a spell, players can't take any actions until you've finished doing so
Even if it was not that many points, it would still be a more worthwhile use of the extra cards than allowing them to sit in a stack
The only time you can deplete the opponents life points is when there are no monsters defending the opponents side of the field and your monster attacks, if your monster attacks another monster with lower attack points or if the effect of a trap or spell card says so
September 2, 2017 Update: And after a bunch of silly Reserved List buyouts-even though I don't care one way or the other about the Reserved List since I am almost exclusively an online player-it would be sweet justice if the Reserved List was, after all the lawyer fear-mongering, abolished
What does wildly increasing mean