Losing all of the skills you gain. No matter how good you get at something, after a few centuries you’ll have lost your edge. You can also only practice so many things concurrently without giving something up. At some point, years down the line, you might try to ride a bike again and completely fail to do it, or try to sing and fail to hit all the notes that came easily before, or do gymnastics but the muscles you need are underused. It doesn’t matter that you spent years mastering every skill, your abilities will degrade over time. You’ll never really be able to feel sure about your own abilities except for whatever you’ve done most recently.
My own experience is that the lower and side areas around the opening going into the vagina are a lot more stimulating than the clitoris, which makes penetrative sex so much better. This is not very common for women, but it might apply to your partner. Applying gentle pressure to these areas is good for me so that could be something to try. Gauge her reaction. I believe this preference is very uncommon, and I’ve had partners refuse to believe I like it, so I’m not very open about it anymore.