Now that the increase in miles has been announced, it might not be a bad time to spend some miles if you can find a good use for them. The last time F9 devalued their miles (a couple of years ago when a domestic RT went from 15,000 to 20,000) I burned my entire account down to about 500 miles before the change went into effect. But, since I do fly F9 a fair bit, and credit my random Airtran flights to F9, and have the credit card, I've since built a fairly healthy balance back up.
I'll certainly be looking to book what I can at 20,000 before it goes to 25,000. But I'll also certainly keep the account, as I (for now) expect I'll continue to fly F9 at least sometimes.