Yesterday evening, I ran my final long run, and from now on, its taper time. I ran a distance of 34.75 KM as per my Polar RS200SD footpod, which would translate into actual run distance of 33 KM, given a 5% calibration error (my 21K at Vodafone half was shown as 22K). Total time taken was 3 hr 58 mins. The first 7K were extremely tough and all the time I was thinking about whether I will be able to finish the complete distance. The next 14K were the best with little or no fatigue, and then gradual building up of stress in my legs for the last 12-13 kilometers. My legs were still strong towards the finish, and I ran the fastest pace during the last 1.5KM stretch to complete the run under 4 hours.
So, overall, things look pretty good. I was thinking of doing about 2 KM more yesterday to make it a round 35 KM, but it was late in the night, and I was anyway over the scheduled distance to be run (32K). My earlier estimate of a 4:30 finish now seems a stretch, and I would be happy to do the run under 5 hours. I would also try to work on my speed, and that should help me to cut time, since I am doing good on the endurance front.
BTW, this was the longest I have ever run, either in practice, or in a marathon (yes, I ran less that this in the 2006 Mumbai marathon, the rest I walked). The last time I ran a 32K in practice was in 2006, and I had done that in 3:57, and I remember that I was really drained out towards the end of that run. Running the last few hundred meters was the biggest challenge then, while in my 33K run yesterday, the last 1.5K was the strongest I ran, and even after that, I was not really busted.