A new pair of pointe shoes lasts me roughly one full-length performance. In rehearsal season I go through three or four pairs a week.
Every dancer has a ritual. Mine is darning the platform, cutting the satin off the tip, a drop of shellac inside the box and then bending the shank until it gives exactly where my arch wants it to.
If you are starting pointe, see a professional fitter and listen to your teacher. The right shoe is the one that fits your foot, not the one your favourite ballerina wears.