It is surprising what you can do when in a group. IMO you need to force yourself to ride 5-6 days in a row no matter how tired you feel and even if the rides are less than 1/2 distance of your event. Do this for 2 weeks, take an easy week, Do it again for a week. DO NOT train very hard the week before your ride. Try to start these rides about the same time of day as the event rides which will mean early.

Not saying the other advice is wrong mind you. There is nothing that hardens you like riding nearly every day. Make all of these rides at your endurance pace or if its a really short ride you can step on the gas just a little.

You can do this.... most of these rides have a lunch break so keep that in mind... 60 miles = 2 30 milers.