Talents
 

My friend was just asking me,

If you, for example, were Fire specced, and got Dragon's Breath (Rank 2), then switch to Arcane. But find out it's crap, and change back to Fire...

Will you still have Dragon's Breath (Rank 2)?

Nope. Whenever you get your talent points refunded (for any class) you lose any spells that you may have trained to rank up those talents.

why im sticking with fire after changing from frost , too much gold wasted.
both talent tree's have their bonuses and negatives and both are equally effective.
i found frost to be good for a more controlled fight while fire is far quicker though more mana intensive.
im level39 now and my major choice will be , when i reach level 60 or so , which two trees to mix?
arcane + frost
arcane + fire
fire + frost

It totally depends on your playstyle and what you'll spend most of your time doing. What was said in the other thread was true - there's no right or wrong answer to your mage talent spec, it's just about how you play.