Pointe is rough.  There does get a pointe when you need to know when to take them off.  You can't keep dancing and ignore the pain you are in.  Trust me, I learned that the hard way.  You have to be careful with your feet even if that means taking your pointe shoes off early, then take them off early.  I have been doing pointe for five years or so and I know a thing or two about my own personal limits.  Personally I have a rule that I like to call three strikes and take them off.  If I have to take my pointe shoes off three times during class to readjust them, and I am in pain, I take them off.  There are a couple of exceptions to the rule however, if they are new, then I can readjust anything.  Also if an old injury is being a pain and it has been lasting for more than five or six combinations, then I take them off as well.  Injuring yourself just because you are stubborn and don't want to take off your pointe shoes is kinda dumb and I will admit that I have done it before.
  During an audition, my bruised toe was really bothering me on pointe and I just ignored it and kept dancing, gritting my teeth and dancing through the pain.  When I took off my shoes, guess what, my toe got worse and the next week I didn't do pointe.  So learn from my mistake, learn your limits and do your best not to go past them and hurt yourself.  Anyways, have a great day and just keep dancing! ~Mia