Howdy,
Since cactuspete and others have echo'd what I'm heading to say - feel free to skip me if ya like.
I personally enjoy using my miles for the more expensive tickets, for example - given the opportunity to use 200k miles for 4 tickets in F to HNL - I jumped at the chance (this includes a few days in LAX, a few in HNL and a week in KOA). The way I figure it, I got over .06 a mile in value.
My advice, instead of worrying about how to hold on to them is to use them. (Now, if you are one of those who wants to 'bank' your miles for the future - I say spend 'em now and throw the $$$ the tickets would cost into the bank).
Just my two cents.
Keep the faith,
Pakse