Honestly? Forget it. You've left it too late. The SDW is too hard to be starting training for now if all you do is 2 – 3 hour rides. I'm not being nasty, but really you're not going to be in a happy place for most of the ride, and if you can't enjoy it what's the point? Either aim to do this next year and work out a proper traing schedule, or if you're detirmined get your head around the fact that you'll suffer.
Ha ha. You're not serious. Don't get me wrong, it's double hard, but my longest training ride before doing it was only 50 miles and I didn't die.
Did it in 14 hours – to be honest i'd put in more training if I were doing it again, if only because the hills at the end are quite tiring. Just to add to that, I probably will do it again this year, but due to a snowboarding injury I've not ridden for the last month so i'll be starting from a pretty rubbish fitness level. That being said I intend to knock a fair amount off 14 hours, largely by just MTFU. I wasn't even considering starting to train for it until may. That'll be loads of time.