I think Alan’s absolutely right. You definitely need to work up to longer rides. There are things which only become apparent after a couple of hours, and you’ll need to be thinking about food and nutrition as well as comfort on the bike.
What period are you doing the L2P over? What sort of pace will be expected? You might need to look at doing some speed sessions too to push up your overall pace (that’s if you’re doing one of the 24 hour L2Ps)