How long bioethanol fuel lasts depends on what you are using it for, but if you are using it to fire a bioethanol fireplace, which is a very common use of the fuel these days, then bioethanol fireplace manufacturers have some answers.
Bioethanol is sold in litres, and it is also normal for bioethanol fireplaces to have burners with a fuel capacity of one litre, so when you ask the question of how long bioethanol will last, it is generally best to think in terms of how long you can keep your beautiful bioethanol fire going with one litre of bioethanol fuel.
Actually, the estimates here differ quite a bit, due to the variability of the amount of ethanol used when a fire runs at different settings. The maximum setting on most ethanol fires is usually not used for long periods of time, as it can get too hot for prolonged use. However, if you run the average bioethanol fire at full speed, you will get somewhere between 3 and 4 hours of heat per litre. Manufacturers estimate that you can double this on lower settings, giving you 6-8 hours of use from a litre of bioethanol.