Hi there. Firstly, I'm not sure what a smartsmoker pack is, so I've taken a guess that it is something sold by this company -
Electronic Cigarette Starter Kits | Smart Smoker UK From your description of multi piece cartridges, I'll assume that it's the "mini" type, which looks rather like a
DSE101 model. Note there are much better models available for the money. A Joye eGo is a good example which will perform a lot better than a DSE101.
With that type of e-cig, the liquid that contains nicotine (
e-liquid) is held in a small inner cartridge (looks like a small cylinder) in the mouthpiece, which holds a small amount of white filler material with the liquid soaked into it. Some companies claim that a cartridge is equal 12-15 cigs. This is a lie. These cartridges hold perhaps 0.25ml of e-liquid, and the manufacturers claim this is equal to 4 cigarettes, although it's arguable even that is optimistic.
If you remove the inner cartridge it will continue to produce "smoke" for a while. That is any e-liquid still held in the atomisers' wick. Eventually it will start to burn off any deposits on the atomiser coil, which will produce an unpleasant taste. It is not good practice to vape an atomizer dry, as it can kill it.
No experienced vaper will buy pre-filled cartridges and use them alone. The reasons for this are quite simple. A small 5ml bottle of e-liquid, which can be found for just over £2 in the UK, will refill one of those small cartridges 20 times. A 30ml bottle is equal to 120 cartridges. Now look at how much that company charges for cartridges. You also have a much wider range of flavours and strengths. So buy some e-liquid.
Once you have a selection of e-liquid you will not be worrying about getting every last drag from the cartridge, simply top it up as soon as the vapour starts to die off and before there is any "burnt" taste.