Training for specialized events be it in cycling, running, swimming etc. usually has to mimic the race. For something that long you'd want to recreate the duration though with slightly less intensity lest you overtrain.
If I was you and training to do another one I'd figure out how long each pull was, what the avg wattage per pull was and avg duration and intensity of each rest period then recreate that in training. Probably keep my wattage to 95% of the figures from the actual event and start the new training period at about a two hour ride, working up to five hours several weeks from the event and then start to taper a couple of weeks out.
I'd limit myself to one of those rides per week and do an LSD ride every week as well. I typically work up to LSD workouts of 125-150% of the expected duration of my target event. Between those two rides alone you'd be doing close two 12 hours a week, personally I'd probably stay off the bike other than a couple of short recovery rides in between.
You also have to consider the possibility that your nutrition wasn't up to snuff and/or you physically just won't be able to ride at that intensity no matter what you do. You may have to pull a little less hard every time to make it through 5 hours and remember that a 5 hour ride with a 42 kph avg is pro tour speed.