How long does a 6 cell battery last will depend on the type of laptop that you are using. Smaller laptops like the notebooks will use less power and the battery will last a longer time. However, with average laptops a 6 cell battery will last for 5 to 6 hours. The life of a battery charge will also depend on your usage. For instance, it you simply use the laptop for simple programs like Microsoft office, then it will last a longer time, but if you are listening to music, watching videos of playing games on your laptop, it may lose its charge in about 3 hours.
Usually battery suppliers and laptop retailers make tall promises regarding the battery life. You should keep in mind that if a shop owner has said that the battery will last for 8 hours, you can expect only 6 in real life situations. How long does a 6 cell battery last before it needs to be replaced also depends on the usage. However, under normal circumstances a 6 cell battery can be charged a 1000 times before it goes out completely. Again battery suppliers make tall promises about the time needed before replacing a battery, but a 1000 recharges are the maximum that you can expect from a 6 cell battery.
Some people try to convince you to buy batteries with more cells as there are 9 cell, 12 cell etc batteries available in the market. It is true that these batteries last longer than how long does a 6 cell battery last, but they are not so necessary unless your laptop usage is really heavy or you have a laptop that consumes more power than normal. You need not opt for the batteries with more number of cells because they cost more and are normally not needed.
Many people have the question that how long does a 6 cell battery last if you recharge it repeatedly before it is completely drained. Well this question was valid with earlier batteries like the nickel cadmium batteries which had a memory effect. In these older batteries, you had to ensure that the battery had drained out completely before recharging it. Otherwise it would have an adverse effect on the life of the battery and repeated recharges before complete draining would cause the battery to get drained even in as less a time as 15 minutes. However, this is not the case with modern day batteries, because all electronic devices nowadays use lithium ion batteries. These batteries do not have a memory effect and can be recharged even before they are completely drained out. It will have no impact on the longevity of the battery. In fact you can even keep your laptop constantly plugged into a power source if it is available with no adverse effects whatsoever.
In order to understand how long does a 6 cell battery last and how to increase the life span of your battery you can conduct some research on the internet. There is a lot of information on the internet about how to make optimum use of your battery and get the best out of it.