640,000 Miles is Right for Me.....
Personally, I don't worry too much about the dreaded "devaluation". Seriously, the *A award chart hasn't changed that much in recent years. That said, I also ONLY use my miles for F or J Award seats.
While some award levels have been inflated in recent years, the quality of J has also improved on many *A carriers. Thus, while I prefer F, I'm now comfortable saving a few miles and taking the occasional J seat on many carriers.
So, for me, the magic number of miles to maintain in my account is 640,000. Given that most any F award on *A is 160,000 RT, I can get one for myself and a traveling companion for 320,000 miles.
I like to have double that amount in case:
1. I have to use Standard versus Saver (dreadful prospect)
2. I need to book two such trips simultaneously
3. I'm undecided on routings/carriers for a vacation so I need to "double book" so that I can "trip improve" on the routings/classes as the months go by.
Less than 640,000 in my account and I get a little nervous...