Ah, yes, that's true, it's so stupid of me to think it, I realised it just a couple of minutes ago myself. What you say is absolutely true. But for some weird reason my DPS is always lower when I do that! I'll try it over a longer time span! I used to do it for like 10 minutes. I must say though, I really don't think I lose time when pressing Fire III during my last fire III. My reaction is really fast, but I guess it does accumulate and your theory is correct. I don't wait for the proc icon to appear though, so I don't think I lose time when there is a proc. Basically it will be like a naturally casted fire III proc. Cheers for clarifying, I was silly on my reasoning! I'll test it out tomorrow.
I use Blizzard I when I know my mana will not have fully returned when I'm about to use Fire III (Blizzard III - Thunder II - Blizzard I (in case of not enough mana regen) - Fire III