Technically, yes, although it's more of a habit by now.

Duke's right. I suppose I could use the eleth in me but that poses a few problems.

The first is that I don't have an abundance of any one type. It all evens out. Using up one type in a spell could cause some damage, especially if there wasn't any around to restore it.

The second is that you can cast much stronger spells by using external eleth. Living things contain enough eleth to survive, but you can achieve much higher concentrations of it through cryas crystals or proximity to the valkines.