Hi . . ,. I've been slowly trying to 'remember' that I have those extra keys :-) after so many years playing 71-note arrangers. I do use the top keys a moderate amount, mostly for piano 'runs' to be able to go a bit higher. I don't use the bottom-most keys much, but in a few songs I have found ways to use them. Not often, but here and there (and maybe a bit more as I discover songs for which some low notes (in addition to my chords) are useful ...

Jim