Ah, sweet and savory is the irony of the Lord that we who were once hormone filled teenage boys now have to face the fact that those same hormone filled teenage boys are now the enemy. Surely God knew just what he was doing when he gave us daughters.
As the specifics, I would look at it this way. If this is a good boy and your daughter truly loves him and the sincerely want to get married some day then by disallowing him to spend the night, you are protecting them both. If perchance they did fall to temptations, and hormones will be raging, then they both have to face that fact and acknowledge it.
Just think, you have given your daughter a proper upbringing and helped her form a good conscience. Now because of wanting to be nice you have allowed her to fall. With her good conscience she will feel less than pure and will eventually form resentment towards you, the boyfriend or both. A lifetime can be changed for the worse, several lives could be damaged and the boyfriend who either becomes the husband or not will always regret that he didn’t make the hours drive.
Protect them, let him go home. Offer to buy breakfast the next morning safe in the knowledge that you have done the right thing and that in her heart your daughter knows that and loves you for it.