To answer this part, the earlier in the calendar year, the better. If you qualify anytime between Jan 1 and Dec 31, 2015, the status is good to Feb 28, 2017. So a January qualifier enjoys ~26 months of status; a December qualifier ~15 months.

But you can't really game this. The qualifying counter resets each January 1, so it's not as if someone with 99K miles in December 2015 could wait until January 2016 to fly the last 1K miles; rather then getting EXP through Feb 2018 for qualifying in Jan 2016, they would find themselves with PLT status based on 2015, and just 1K miles towards the next year's qualification.

(This applies to normal qualification; status challenges are a bit different).