3M water filter

[Kmann]

Have read quite a lot here about the water handling, but I am still uncertain how to handle it.

How long can water stay in the tank (during a warm summer) before its undrinkable?

Did anyone actually fit the 3M E2 water filter? Would that be the easiest way to clean drinking water from the tank at all times?

Or how is water tank routines at the best?