It sounds like you're letting them get dry. You have to keep the atomizer wet or it will burn it out. The pre-filled carts/cartos don't last that long and will burn when they get dry. You really should invest in some juice and use that instead of buying the pre-filled ones. IMO, the pre-filled cart/cartos are a complete waste of money because they get used up so quickly.
They have their place, I use a lot of pre-filled cartomizers. The ones from liquidXpress rock. I look at it this way, I can start with a fresh carto at 7am with my coffee and it usually last me till late evening. Yesterday my liquidXpress grape (Yum) lasted the whole day and I am still hitting it right now.
I pay 8 bucks for a box of 5 so thats $1.60 each. So yesterday I spent 1.60 instead of $9.00 (Yes Camels or Marbs are 9 bucks in NY) for a pack of analogs. I use to smoke exactly 1 PAD right down to the hour.
Even if I use up two cartos for $3.20 a day, I am still saving $5.80 per day or $170.00 bucks a month.
Now I do save them and refill sometimes. I drip sometimes too though not a lot. I have no problem burning up two cartos a day, its simple and I am still saving a boat load of bank.
I have tried some other brand cartos and cannot recommend LiquidXpress enough !!! They work great and last a good long time, I have counted and they are 180 of my size hits.
Sometimes I go 7-10 days without physically touching any kind of liquid bottle ... life sure is simple like that.
So I guess like everything there are two ways to look at it. Yes I could save a good chunk of change by filling blank cartos or dripping all the time.
But I am Busy/Lazy and I am all ready saving a good chunk of change and I am feeling better too.
The tough part is ordering $50 - $80 bucks of cartos a pop, it seems like so much till I remember the $9 dollars I had to scrape up every single day for my Camel Lights.