It doesnt grow into big roids and its mined before it even gets to 50% max size.
Doh, I didn't know they grow ??? I've been hoovering Kernite up as soon as servers come up Monday and Fridays. Roughly how long does that take ?
Kernite in high sec only happens in Amarr space. if you are going to mine it there certainly don't sell it there as it is obviously selling lots cheaper in Amarr space, which Tash is. Check
market prices and get it hauled.
There are a lot of systems in Tash with Kernite - Paye is a decent one with 13 belts, 0.64sec. Be aware the Goonswarm suicide gankings (they have declared Jihad on miners in HIGH SEC) are happening around here; I've noticed they mostly happen in systems with Ice Fields so steer clear of those and you are prolly safe.
Having said that I agree totally mining Kernite is a false economy, once you get into Barges or BCs. You are constantly looking for the next target. If you are in something only running 3 Miners IIs then its not so bad. Time taken to change targets, get the mining cycle going again and for the part of the cycle you lose when the roid dies means the size of the rocks you are mining is at least as important as the ISK the yield is worth.
Spend a lot of my time just mining Veldspar as its easy to find a near infinite amount of large rocks that you have little to no downtime on.