I think there are several issues with prolonged use. Some may not be as big of issues to you. When you start adding heat to c02 liquid it becomes even more runny and tends to look for any escape route it can. Eventually from pocketing or just casual manipulation of the cart you will see they can generate leaks near the bottom at two locations. One is straight from the heater air inlet(s). The other leaks will come after more than 4 uses would be at the transition of glass to metal. Eventually you may get some throught these areas and it sucks when you have a cart that has almost as much oil on the outside as it does on the inside.
Leaks dont necessarily haooen after 3-4 uses IME but more sk around 6-8. I suggest changing them at 3-4 refills based on my experience of the liquid getting darker as you get further through the cart. You rarely will deplete all of the liquid in your cart so you will be adding fresh clean tasty liquid to something that has been already cooked some due to heat and vapor running through it so much. By 3 or 4 the cart might just look really darkd with a fresh refill. The taste will suffer a good bit at this point and I feel like the strength of the liquid gets diluted more so now you have a less tasty and less effective experience. I personally would rather spend the $8. You wont know until you try and experiement tho. What it is for me it is for me, but your experience is all yours and may be very different then mine. Time to get out your log book and make some notes! Dont be afraid to get scientific
