Earning the miles is just a means to the end more travel ... however, I'm always reluctant to spend miles because I always thing there will be a better use for my miles right around the corner. In the past year and change I've spent our (me + girlfriend) miles on:
2 BC tickets on UA to HNL + 5 free nights at the Hilton Hawaiian Village (PiP Express & PiP ... the best use of miles ever for me I dare say

)
1 FC ticket on Swissair MSY-BCN
1 BE ticket on DL MSY-BCN
1 BE upgrade on DL CLT-LGW
This compares to having spent my miles previously on domestic FC upgrades and coach tickets. I learned the best use of my miles is in the longer journeys in premium classes of service