First Post and Cart Questions

Hello all.

I have been reading this forum for awhile, and just registered today. First off, I got to say all the info on here has been very helpful. Thanks!! Though, I want to talk about the carts a little more. I know they seem pretty hit or miss (and usually miss), but i already went through 8 carts in 32 hours, which 2 of them completely failed on me. I have removed the foil, didn't remove the foil, fluffed the wool, and any other crazy idea i could think of. So, I bought some liquid from ELP, and here are my questions:

How "long" do the 10ml bottles last?
How much do you use if you refill the carts, and do you have any leaking issues?

Other than that, I ordered my liquid last night around 11pm, and it shipped out today!!! AMAZING!!! I ordered my blu 2/12 and got it 2/23 (shipped out 2/20), so a bit better ;-).