Figuring out the best time to do it depends on your deck, what your opponent might do, and what you want to achieve
Nibelheim Aflame OK, Nibelheim Aflame is a little pricier at around $7, but its still a great card for anyone looking for an aggressive spell that you can play from the graveyard, too
For Winter Orb, this will be artifact and creature sources of mana that continue to untap regularly, or a way to tap the Winter Orb so that it's not untapped when your turn rolls around, and you aren't effected by it, like Urza, Lord High Artificer or Derevi, Empyrial Tactician or the new Galazeth Prismari (there's no rule that says you can't generate mana you can't spend, and if you think this is a hint about a forthcoming article, then, you're right) A Stax deck will also need a win condition, since it's not enough to merely grind the board to a halt
Most recently, Maui - Half-Shark could be found in a good amount of decks that were used in the DLC held in Melbourne, Australia earlier in February
Obviously you always want a Brainstorm, I just passed one in the draft quite early and lived to regret it
Still, casting a turn 3 Tibalt, Cosmic Impostor is a dream very few people have accomplished