OP, I think the reason women get their hair cut is that they can't sustain the long growth and it's going grey, not because of some magic age line, after which you have to have short hair.
I plan on keeping my long hair, and I'm in my mid 40s. I have some grey at the temples, but see a lot of friends who have gone completly grey and gone short so they can colour it without it looking like a dried up bush from the hair dye.
If you don't need to Colour it, then keep it long, and if it's thick and bouncy, it's not eniviatable that it thins and looks straggly- they happens to some women because of thyroid problems, or hormonal shifts with the menopause.
If your hair is thick and shiny and bouncy and you don't need to dye it, then wear it long forever- A lot of my aunts had long, strong and not grey hair into their 90s. They didn't need to cut it, so they never did. It was fab on them.
There are no rules about hair length and age.
If you have thin, wiry hair going grey, then it's proabbly easier to get the chop so that it can be dyed and kept in condition by trims.
You sound like your hair is in top condition, so leave well alone and enjoy your healthy mane!