I screwed this up a little, by misunderstanding my insurance benefits and underestimating how quickly providers will deliver bills. We have care from the first week of January, that hasn't even made it through determination of benefits, let alone provider billing. Combine that lag with the general uncertainty in medical billing, and my effort to maximize the benefit missed.
This was a calculated gamble, and so far we've only blown past the max by $60, but I have a little FSAStore regret :)