I'm of the opinion that a mini (DSE901) will last about 3-5 cigarettes worth with either the original style cartridge or the new cartridge, with the interim size cartridge it's down to 2-3 worth. I use 4 or 5 carts a day with mine, sometimes more
In the penstyle I use 1-2 carts per day generally, sometimes 3, and was previously a 20-25 a day smoker, so somewhere in 10-12 bracket is how I'd assess the pen cart.
Super minis are only about 1-2 worth and are really far to small in my opinion. I've given up on mine out of sheer frustration with it.
Hope that helps