
I'm playing an Elementalist and she's using:
Rodgort's Invocation, Searing Flames, Liquid Flame, Glowing Gaze (of course Fire Attunement, Glyph of Lesser Energy too). Pretty much the basics on area of effect spells and I can say I'm having a LOT of fun seeing all those 100+ numbers coming up when I cast my magic.

My question is about Burning durations, as I'm getting a little confused and I need to know it to use SF and GG better.
Question: Suppose I hit a group with RI, they start burning for 3 seconds. If I follow up with SF, they'll all take damage, but will the burning duration be increased to 7 seconds (SF duration)? Another example, suppose I hit with SF first (they take no damage but begin burning for 7 secs), my follow up SF will reset the burning duration to 7 seconds, or just do the damage?
From my observations it is not refreshing the burning duration, but I'd like to hear from the most experienced. I'd appreciate hints on increasing burning durations please. It really helps the damage and my energy management with GG (even though my Energy is on the 90's, I sometimes still run out).
Thanks much.