Hello everybody !
I have the following situation in few hymns (SATB) I'm typesetting :
I chose to use the lyrics extender when for example, choir singers have to hold a long note on a phrase ending, especially when, for example, one voice sings a half note while some others sing 2 quarter notes.
I thus use the extender to remind all singers to hold their note till the end, else the voices singing the two quarters will be heard alone.