Disposables will often specify have many puffs they're designed to deliver. Towards the end of its lifespan flavor and clouds will begin to drop.
The beauty of a disposable is that you don't need to every worry about how much charge is left or when it needs to be refilled. Sometimes as small a single cigarette they're perfect for vaping when on the move.
They can be stored for 12 months without issue. Use either as a super convenient and portable every day vape or buy some just to act as a backup.
Have friends that smoke? Why not hand them a disposable to show them just how much better it is to vape. No smelly smoke, no need for a lighter just delicious vape juice flavors and a satisfying throat hit.
When buying a disposable you should ask yourself what your requirements are. Do you want a super small and portable vape? Do you want a larger disposable which last longer (charge and puffs)?