Hey Capn,
Good luck. For starters it's important to know that just because there may be a lot of words in the question and because it may be a 5 pointer doesn't mean that it's a long drawn out question. Indeed you may get a 3 pointer that's got 4 or 5 (planned or actual) ETAs and GWs at different points enroute, the reason it's only a three pointer is that they know you don't have to do a climb or as many sectors.
Here's a breakdown that I compiled based on what I came across (I sat it twice) and what people told me to expect (corrected to equal exactly 50 points in 17 questions):
5 pointers X 3 or 4
4 pointer X 1
3 pointers X 3 or 4
2 pointers X 8 or 6
1 pointers X 2 or 0
If you assume the above and aim to do questions under the following maximum times:
5 pts < :25
4 pts < :15
3 pts < :09
2 pts < :04
1 pt < :02
you should come to < :180. Those are figures from before I made my second attempt, the only change I would make now is to aim for :20 5 markers (if one of them takes you :30 though that's probably OK) and probably allot a bit more time to the 1 pointers. What can save you (this is according to my experience and that of a mate) is getting at least one 5 or 4 marker done in 10-15 minutes, if you do that then you've just scored some extra time to devote to 2 tricky 3 pointers.
As far as preparation goes don't waste your time doing too many 2 or 3 pointers, just hammer out lots of the 5s (the 1s, 2s and 3s are mostly based on portions of a full flight plan). Arrive at the exam early enough to do a simple flight plan (not a new one, choose one that you've done a few times) just to go through the motions and stretch your brain out in that special Flight Planning way.
Good luck again,
FRQ CB