Congratulations on being able to increase your mileage by 30.
I am prepping for the HHH 100 and have been increasing mileage increments by 10 mi. For each subsequent ride the previous high mileage was fairly easy; then the last 10 mi got hard. Maybe my advanced age of 61 won't let me have as good results as you did.
I am guessing I will need to comfortably do 85 mi before my first century. I am currently at 61 mi. I am glad I have until August 28.