I think that we're lucky these days in that there are fewer "rules" about what people should/shouldn't do at various ages.
I remember my mother getting her waist-length hair, which she wore in a beautiful French pleat, cut and permed because she'd turned 40.
She suddenly looked like all her contemporaries and far less elegant than she had.
If she'd done it because it was far less faff than putting up masses of hair every day, fine, but the reason was that "old women" - at 40! Argh! - shouldn't have long hair.
So I don't think there's a cut off point for sleeveless tops either.
However, speaking for myself and myself only, I generally like to accentuate my positives rather than my negatives.
So, I wouldn't wear a clinging Jersey dress because I have a classic menopausal stomach. I would wear short sleeved tops if I wanted to because my arms look okay to me.
As it happens, I don't tend to wear them because I burn really easily so prefer to cover my shoulders.
I think if you feel happy and comfortable in them, you should wear them.
Actually, on reflection, I did get upgraded on Eurostar because "Aww! You've got a little baby in there, haven't you..." so perhaps I should wear stomach-emphasising dresses when I'm travelling!