Charm makes them Friendly.
It lasts quite a while.
I like BrB's answer for when it expires.
Hypnotism improves reaction by +2.
I don't think it would stack, but perhaps an argument is useful.
In any case, when the spell expires:
"Even after the spell ends, the creature retains its new attitude toward you, but only with respect to that
particular request."
OK ... it's cheese time
Charm + Hypno as X-codes said, equals Fanatic, but it'll jointly expire.
"particular request" has to be worded (and worked out) to receive
another Diplo attitude adjustment.
Intentionally flub the next Diplo check, but not a total fail.
** Only to make the attitude adjustment stay the same !!
Hypno expires, but doesn't have anything to do with current attitude, caused by latest Diplo check.
Charm expires, and also doesn't have anything to do with current attitude. caused by latest Diplo check.
If this is too cheesy (and it is soo creamy and gooey)
the "particular request" just has to be allowing the Charm + Hypno again.
: "You tricked me ... and I liked it."
EDIT ... and then there's the Half Fey racial class.