lol, ive never changed a cart really. I've tried changing it after a few weeks, but it was no different, so i just use the same cart. the only thing ive ever done is take out the filler in my 401 and press it in a tissue because it was all brown looking. the tissue soaked all the brown out, was good as new again, so i kept going with it. cant say as ive gone much over a month on a cart since i have moved from a 901 to a 401 to an em-901, but i have gone over a month on both 901 and 401 carts, and they still work like the day i got them. dunno what you people are doing to your carts

smokin em dry or something i guess, lol.
p.s.- i do rinse my carts by putting
juice in it and smoking it out