You should be able to get through 3 tankfuls with Legend.
Good to know.
You know.... I am going to go off a bit here... I am, and my wife would certainly be the first to agree here

, have (expert) opinions on most everything. And when dealing with 'microcoils', cotton is a more superior wicking medium than silica. I don't know of any raw data, but my anecdotal evidence is that, while silica may wick
quicker than cotton (per unit wick, if you want to call it that), cotton holds a significant amount more of whatever liquid you are trying to transport. And juice capacity, not wicking speed, is critical when you are dealing with microcoils since, near as I can tell, neither cotton OR silica can wick enough juice to keep a microcoil wet over an extended amount of time.
Microcoils is a misleading term. They are, in fact, massive when compared to the older style, spaced out coils. They tend to be 10 or more wraps of some very thick, low gauge wire, where the 'traditional' coils tended to be 5 or 6 wrapped of thinner, higher gauge wire. That's a lot of wire there to heat up and vaporize juice. The vaporization functions as a coolant for the coil and as long as the coil is 'juiced', the coil temp won't get too hot. If there isn't enough juice to vaporize, the coil will begin to heat up.... and could hit the point where the vapor starts to oxidize (i.e. burn). That's bad juju.... you don't want that.
Now, back to cotton. Anyone who has used cotton wicks can attest that cotton soaks up a ton of juice. That's a big reservoir for that microcoil. So when that fires, even if the cotton couldn't necessarily keep up with the vaporization, there's enough in there to keep the coil 'wet' until we stop taking a puff... then the cotton does its job and sucks more juice in... refilling the ol' tank. This is where I think cotton works much better... and why I couldn't get a silica wick to work a damn in my KFC. The silica would start to dry out too quickly and I'd get a flavor that would best be described as 'ode to ashtray'.
Now, for the older style coils, like a 5 or 6 wrap of 32g you'd see in something like Protank or Viva Nova, a silica wick may outperform cotton since the juice demand might be low enough to where it can draw in juice fast enough to replace the vaporized stuff. When I dabbled with cotton wicks when I vaped Evods, this is pretty much what I found; I'd burn cotton wicks where the silica wicks would vape like a boss with even the most heavy-handed draw. It wasn't until I switched to RDAs that I finally understood why people were raving about microcoil/cotton....
Now, the big drawback of cotton is that if it dries, it dies.... it'll burn quickly. But it holds so much juice that it can take a while (in my experience) to get to this point, even in something like a RDA. In my KFC, there's no worries as there is no mystery as to how much juice remains... so as long as you didn't choke the juice channels, you're golden.
OK.. done rant....