Hey jes, welcome to ECF!
E liquid is a consumable, like the gas in a car. It doesn't evaporate per say but is vaporized by your coil (aeresolized actually, technically).
As you vape, the level will drop until you need to refill.
What kind of PV (personal vaporizer, ie e-cig) are you using? Depending on your device, you may be able to see the e liquid level (I'm assuming that's not the case with what your using due to your question). That being said, as your juice level gets low, you very well may experience a change in the vapors taste and/or production signaling you that it's time to top it off.
Congrats on quitting the cigs, I tried
vaping as a last ditch attempt to quit myself, about 5 years ago. It's working out pretty well for me so far, I'm thinking it just may have done the trick