If you are in a marriage nagging comes with the territory. It isn't a quality of being in a FLR, but rather a byproduct of being with someone for so long. That it just happens whenever they do, or don't do something that annoys the crap out of the other. Just a fact of life lol.
Nothing anyone can do about it. It just intensifies as you get older on both sides, but being in an FLR relationship is still worth it. All balances out in the end.