I've never been high maintenance but have had a moderate amount of fucks to give about how I look. I have been lucky to look decent with good skin and naturally slim, etc, so haven't had too many challenges.
However, I don't think this is so much about getting older (I am 50 this month), rather an absolute growing inability to keep giving a damn. If I look decent and clean and look after myself, I am getting less and less arsed about previous efforts to keep up.
Example: my nails. I always bit them, from childhood, and regardless interventions, it always came back. I have always been ashamed of them and hidden them or worn false nails. After a severe period of stress I actually bit them down so badly that it disabled me with pain. I am so tired of patching them up and am happy to go forward with short, clean nails that I hope to repair. I am tired of being embarrassed.
Another example: my hair. It's longish and blonde, naturally. It is a good head of hair but naturally frizzy. I am sic of hiding this, I hate curly girl as it isn't curly, and tired of straightening as it isnt straight either! I am hoping to just quit altering it and embrace it's natural, healthy if fuzzy state.
I am also fed up of caring about clothes. I wear moderately expensive, well made stuff, and can't see myself embracing high street offerings, but I am happy now to just have a very small selection of practical stuff that's ok.
As I get older I am admiring more and more women who are my age upwards who don't give a fuck. Like many men, they don't spend money on unnecessary skin care, or over think their clothes. They radiate who they are, rather than hiding it, even of that is plain or a bit wild. I just don't care what people think any more. As long as I am presentable I am more interested in who I am and what I do. I was never ruled by male opinion, or anyone else's for that matter, but there is this weirdly liberating thing here that has really changed in me.