Brake pedal can be pushed nearly completely down to the floor when standing

[ffl]

perhaps it could be like that. when the car is not moving it's possible to slowly push the pedal all the way down when applying enough force.
it's way more force that is necessary to hold the car in place.

when driving, the brakes work like they should and there's no problem.

is it really necessary to already change the cylinder or can i leave it like that at the moment? i mean normal braking is no problem even when braking very slowly, also hard braking when driving is no problem.

by the way, how long does the hydro boosts accumulator hold the pressure to get brake assist when the engine is not running? is it only for an short time, say 10 minutes or does it last for a much longer time, several weeks or so?