I have a piece of (bass guitar) music with some repeats in it, and a direction "last time ad lib. sim.". For how long should this direction remain active? Until the end of the bar? The end of the phrase? Something else?
Since it states 'last time', it'll be until the piece is no longer audible, either finished with double bar line/pause/fade.
Until something more specific is notated, or the piece ends.