One of the things I know for certain is that children grow up fast (even if it doesn’t feel like it while they’re little), and before you know it they’re on their own.
It’s so hard to make sure you’ve taught them everything you want them to know before they leave home. Here’s an interesting article, “What I Would Tell a High School Graduate Today,” that touches on several subjects that your teens should consider. Give it to them to read, or read it yourself to get ideas for topics to discuss with them before they leave the nest. It definitely makes for worthwhile reading.