From what I've heard it is really hard to fully clean a 5ml carto. Just make sur eyou have enough on hand. Luckily they sell them separate (I think). Personally, I stock up so that I always have some spares not being used. When I break into the spares I buy more spares.
As far as how long they last I have no idea. I haven't actually used them. Sorry. I only use tanks on my Ego.