Don't forget clearcasting. That alone drops the average price of a spell by 10%, and it can be used on expensive spells after proccing on cheap spells.
Rank 7 Scorch is a 1.5 second cast time spell that runs at 100 mana/sec. If you cast 10 scorchs, you can assume that you will get a clearcasting. This ends up being equal to around 75 mana/sec if you use Arcane Missles, 65 mana/sec if you use Blizzard.
Assuming 260 spirit, a reasonably achievable value in cloth, you get around 18 mana/sec while casting. With 7k mana, that gives you a nice two and a half complete minutes without stopping, a pretty good number, longer than most fights tend to last, and just standing during the downtime would give you a good deal of your mana back.
That, of course, ignores the bad habit of Clearcasting to proc on individual waves.
The idea, I'd think, wouldn't be to last forever, but just to last til the next Evocation cooldown... much more feasable.
Rank 7 Scorch is a 1.5 second cast time spell that runs at 100 mana/sec. If you cast 10 scorchs, you can assume that you will get a clearcasting. This ends up being equal to around 75 mana/sec if you use Arcane Missles, 65 mana/sec if you use Blizzard.
Assuming 260 spirit, a reasonably achievable value in cloth, you get around 18 mana/sec while casting. With 7k mana, that gives you a nice two and a half complete minutes without stopping, a pretty good number, longer than most fights tend to last, and just standing during the downtime would give you a good deal of your mana back.
That, of course, ignores the bad habit of Clearcasting to proc on individual waves.
The idea, I'd think, wouldn't be to last forever, but just to last til the next Evocation cooldown... much more feasable.