No, timing is not important and most of us have dropped it.
http://genderdreaming.com/forum/gend...le-timing.html
You can't pinpoint O any closer than that. All the rest of it is totally guesswork and I personally believe (after being on IG and here since 2008) that many people who swear they had a certain timing are completely guessing and are probably wrong.
I got my DD by DTD late at night the day before O day (Shettles boy timing) after getting 3 of my 4 sons with cutoffs. Mine was confirmed by ultrasound so I'm not completely guessing LOL. :)
All timing does is stress you out and raise your testosterone.