Ride your bike, ride your bike & ride your bike....
Continue getting some miles under your saddle to get your legs & body prepared.
When you get to the ride itself it is conveniently broken up with 2 breaks so just think of it as three individual 30-40mile rides. You know you can do that sort of distance so it is then a mental game of putting them together. Don't get hung up on the mileage they tell you - they were up to 5 miles out last year.
Off the bike - you can really aid your recovery time off the bike by reducing the amount of faffing you do.
Write a check list of what you need to do each night before you go to bed so that you can sleep well and have a quick turnaround in the morning.
Personally, I took pots of porridge with me to have in the hotel before the bus trip to the start so I wasn't rushing to get breakfast just before the off.
You may want to try some group riding before the event as well as want ever speed you are doing there is likely to be others about the same speed and it's useful for giving yourself a rest in the bunch while someone else pulls you along. Happy to take you (and some of the other eventees) out for a ride some time of you want.
You will find you chum up with other riders of a similar pace each day and it's worth finding them out the next morning so you can stick together the next day.
Oh & don't forget to enjoy it.
HC