I have only been cycling for a few months and I have found that stretching, resting and eating well are absolute key.
Over the last 8 weeks I do at least one 50-60 miler a week with some 30-35's in between.
This Sunday after my ride I felt good but in the evening and into Monday I was really feeling it. Last night however I felt good after work so when at 28 miles I kept going to do a 43.
I only started at 20-30 milers and they took some effort. You will naturally get faster and go further. Just listen to your body, eat protein post ride to aid recovery. I'm certainly no expert and I'm sure I could do things a lot better but I'm still loving it and am dreading the winter where naturally there will be less time for me to go out.
I signed up for some sportives to build up to, therefore I had to train to build distance. I have the London Bikeathon on the 31st and I'm still pretty sure I don't have the 100 miles in me so rather than looking to do it in one hit I'll take a rest at 60 eat them try and go again.
You'll soon be boosting your distance! Good luck