I'm glad you're happy with your purchase Stratosphere!
2.68 APS is pretty boss for 2 handed builds, even if its only for a few seconds.
You make a good point on the proc. This logic seems to find a common ground between the 3 second and 5 second claimers. I would like to see some other FD users maybe confirm Strats findings so we can get a consensus for the OP.
I've counted it with a clock over two dozen times. Every time it's at least 4 seconds with a few times pushing 5 (strange but true).
The proc is 5% as I stated earlier.
If you think 2.68 is fun, try 4.0+ ;) - I was playing around with a 1.20 Flying Dragon and stacked attack speed.... INSANE.