I can relate to this. When dating, my wife (was gf then) dressed in sexy outfits and wore lingerie. After our marriage, the fun-loving and teasing slowed down. Then, when her daughter came to live with us, it really slowed down.
I think as long as my wife has more thongs than i do, she is alright with it. However, it seems when it comes to thong swimwear, her swimsuits, as she gets older, tend to provide my coverage whereas my swimsuits, as I get older, get smaller. So far, she seems to tolerate my underwear and swimwear.