You also have to keep in mind that when you are flying on miles, you don't earn the miles...so the true cost (if you are flying yourself) is higher. And, you don't get status miles on that either. I burned 160k miles in FC/BC to Asia a few years ago...but the true cost was 200k since I didn't earn the 20k (status) plus 20k (bonus - I am CP) for that flight.

I tend to use my miles for last-minute flights that cost a fortune (used 20k last month to save $804 on a same-day RT for a funeral), and for my companions. When the family flew to Europe last summer, I paid for my and my wife's tickets (so we could use the upgrade certs) but flew my kids on miles (they were happy in coach).

But, of course, YMMV. As others have pointed out, it all depends on your earn/burn ratio and how much personal flying you want to do.