With the current health of the airline industry, and the fact awards usually get more expensive/ harder to get at each program overhaul (witness CO), I try to keep my mileage balance low.

For most non-business trips, I will check if using miles would be 1) possible, 2) a good deal. I prefer $ in the bank to miles with an airline...

Two exceptions so far:
- DL, where 'old miles' are more valuable than new ones. I have yet to redeem any old miles from DL
- KL and its one-time 'mileage comp' offer at the beginning of the year: I sorely wish I had kept a large balance in a program where I had elite status