I was reading another thread on what do to with with 500,000 miles and it got me wondering what is the best strategy for managing your FF miles.

I've always had the thought that I would rather use up my miles (on reasonably long distance award tickets such as us-oz) as I needed to rather than accumulate a lot of miles for an as yet undetermined future holiday flying biz class RTW for example. My reasoning is that you never know what's going to happen to these programs and the miles as well as the time value of money...as a consequence, I've tend to keep the balance in my MP account around 70,000 or below.

any thoughts on the best strategy? is there a threshold of how many dollars per mile below which you wouldn't redeem for an award?