How about this; instead of taking a glass half empty approach to this, let's start with half full. Your man is comfortable with you, so lost in the moment, so uninhibited that the natural sounds of his pleasure are coming through. Whereas before he was more in his head and embarrassed to emote, he now finds himself opening up and letting loose some sounds -i.e a moan.

And now, let's explore glass half empty. Long term sex has yielded day-to-day sex fatigue. What used to be amazing nut-slapping-nipple-thrill sex is now nut-slapping-nipple-chill sex with no thrill or amazement to speak of -- so yes, your man is "pushing" for more.

But,even if we are dealing with more of a glass empty than full situation, it's far from a major issue. On its own his moaning doesn't mean he's grabbing at straws and your sex life/relationship is doomed. It just means he's adding a new erotic element to your mix. Remember your relationship and sex life is a living organism. It needs to evolve and grow; it needs to reinvent itself at times to remain relevant - to ensure it survives.

I've given you some ideas and insights. But that will only serve you so far. The final analysis requires something more: you asking him (preferably not while he's moaning) -- a. he won't hear you and b. he's in the groove or trying to be. Sure, it will be embarrassing for a moment to call him out on his audible repertoire, but don't forget you guys are long term lovers. You can handle some candid moan talk. Once the source is discovered you can figure out if you are actually dealing with a bone moan or bone groan.