I agree that you should take him out on a date. He'd love that!
But beyond that, for a more long-term way to (hopefully) keep his "darling" behavior going, I have an idea for you that I got from a relationship seminar thingy I went to at church.
The speaker gave us an assignment to go buy a dry-erase board and put it up where you and your spouse will see it. Every day, write something specific about him. Like "thank you for loading the dishwasher!" and "You look good in that blue shirt" or anything happy and positive about him. Maybe he'll start writing things on it about you, too.
I am going to do this in our bathroom, where he'll see it every morning. I don't like the idea of a dry erase board because they're not exactly beautiful, so I am going to *try* framing some paper that coordinates with my bathroom decor and just writing on the glass. I already bought the dry-erase markers :)
Good luck. I think we'd all love to find ourselves in your situation!