I didn't read all of the replies, but 15 acres is plenty of land for bowhunting IMO. We hunt LESS than that and we have had 3 at a time out there before. Comfortably.

That being said, I wouldn't have let him, especially with all the work you have put into the last 4 years, ESPECIALLY if he already has another place to hunt. 20 MINUTES?! I'd LOVE to have a 20 minute drive, I have 45! I just don't trust people I don't know in the woods. My husband and I only take responsible people out to our property with us, people we have known for years!