The battery will drain faster or slower depending on what you are doing. Working in a word processor or reading things online will give you much more battery life than say watching movies or playing games. Those will drain it quite quickly.
Also, it depends on the battery. If you are using and OEM battery it will last much longer than an aftermarket one. Those are hit or miss and can even cause issues with the laptop. So I would suggest you not use any aftermarket ones.
Add to this that if you have things running in the background, things you may not even know are actually running, that will also drain it faster.