I start looking for opportunities to use miles when my balance starts creeping up toward 200,000. That is a sufficient balance to handle any "emergency". Once I've made status for the following year, I have no issue with taking free flights. I also use them for family and friends. It would be very disappointing to have a ridiculously high balance be de-valued, knowing I could have enjoyed greater value by making good use of the account. Particularly over the past year, we have enjoyed some wonderful times on award tickets and I don't regret it a bit.