Hi there! Thanks for your post and welcome to the forum.

This question is exactly the one we are all trying to get an answer for. I'm specially interested on this subject because I'm also going to have a long distance race by June this year. I'm going to apply these smart techniques that learned reading Serious Cycling by Edmund R. Burke. Good book indeed!

I have written an article in the blog which tries to get an answer to your question, and I hope it does. Read it here Workouts Training for a Long Distance.

It talks about Setting a Weekly Distance, Set your Training Goals, Making Your Schedule Count and Making Advancements without injuries. Let me know it you have further questions ;)

Sam