i was running out of liquid i got from this smoke shop but since i refuse to go back to him and i love this liquid, i ordered on-line. hot vapes was great and easy to order from and really fast. anyway, when i got the new bottle i noticed a huge difference. the bottle that was almost empty the liquid was getting yellow and thick. the new bottle the liquid was clear and easy to load. we're new to this and didnt notice a change. how long are liquids good for??