I'm aware that this location for Crystallized Fires had been found previously and posted somewhere (what hasn't?) but what I wanted to share with you is something I had to test and find out for myself.
Go to Frostfloe Deep in Storm Peaks. I shouldn't have to draw you a diagram showing you where this is. This cave is north of Camp Tunka'lo and has Wailing Wind wisp mobs inside.
-No set respawn timer- The cave and mobs are for a Horde questline. The faster you can kill them, the faster they respawn somewhere else in the cave. I brought a boomkin friend to this cave and had him kill stuff in the back section. He kills one, another respawns next to me etc. We could barely keep up and at one time almost died to the respawns.
TLDR== Picture the Gothik fight in Naxx. The faster you kill live-side, the faster they spawn on dead-side. Same thing as Frostfloe Deep.
Have Fun solo or with a friend.