Buildapc

It depends on a number of things. Heat kills lithium batteries fairly quickly. A battery will last much longer in a laptop with good cooling. Storing the battery at full charge is not good for it. Some laptops let you specify a maximum charge percentage. Only charging to 80% will make it last much longer. Charging to 40-50% if you know it's going to be plugged in for an extended period of time a good idea too. Fully discharging the battery is a lot worse for it that only discharging to 20%.

If you are not fully cycling the battery daily, you should be able to get 4-5 years if you treat it well.

The Framework laptops are some of the easiest laptops to replace the internal battery on and you can buy replacements directly from them.

Most internal batteries can be replaced provided that you can actually buy a replacement. Some laptops have glue or double sided tape holding the battery in place and prying a lithium pouch cell out is not the safest thing to do.