Store lipstick in the refrigerator. Or store them in cool and dry place.
They will last much longer.
Never use a tester on your lips - it's unhygienic.
Test lipstick on your fingertips - the color and texture are closer to
that of your lips.
If you want your lipstick to last, use pencil first as a base. Outline and
color in your lips with pencil (nude, if your lipstick shade is light) and
slick your lipstick on top.
Your lips will also look softer, "smudgier," and less defined
if you don't use pencils or lipliners.
After application, run your index finger through the middle of your lips
and pull it back out. The excess will come off on your finger, not your teeth.
Outline your lips in pencil before you apply lipstick or gloss if you don't
want your lipstick to feather.