In a spirit of mutual agreement can I also say, just keep going out on the bike. Don't worry about intervals, either sprinting, or up hills.

For a long distance ride or a tour you simply need to be comfortable putting the miles in, which is essentially, riding as much as you can or can find the time to. If you need to ride 100 miles per day, then being absolutely comfortable riding 60 miles in 4 hours is probably enough.

You need to put the time in so you know you can sit on the bike all day long, but if speed is not important then that's all there is to it. Hopefully I've made that sound easy, I know it isn't in reality. Good luck.