The G49 code is not a required part of your CNC program. It is rare that you would want to move the tip of your spindle to an exact location. You will almost always have a cutting tool in the spindle that you will want to account for.
This means the G49 code is not used often. It is more important to make sure you have the correct tool and offset selected.
Some programmers choose to include the G49 code as part of their safety block of code.
Others skip it and just make sure to call out the correct offset for their tool at the start of a new section of code.
As long as you switch to the correct offset for the currently loaded tool then there is no need to cancel tool length compensation with the G49 code.