I can do 10 days comfortably on the overhead hand luggage only.
BUT I wouldn't say I'm really a "light" packer. I'm more a "dense" packer. So into my overhead locker suitcase I can usually fit 1-2 swimming costumes, 2-3 pairs of shoes, 2-3 nighties, a pair of leggings and a vest for if it gets weirdly cold, underwear, socks, a spare jumper, a couple of lightweight cardies and 5-6 dresses, maybe a pair of shorts and a t shirt if I want them, plus teabags, medications, swimming goggles, spare glasses, umbrella.
Then my underseat bag takes toiletries, kindle, chargers, headphones, water bottle, hair brush, sunglasses, waterproof coat, jumper, a big silk scarf, shopping bags and I wear a hat on the plane.
I don't wear makeup except sometimes lipstick which helps, and my hair doesn't need much shampoo or conditioner, so I get away with 40ml of each for up to 2 weeks.
And my style of dress is quite formal anyway so I can definitely wear stuff for the evening that I wear in the day. I usually get a couple of evenings out of a dress and then downgrade it to day wear, as that way round you haven't sweated into it.
Ultimately I am motivated by not wanting to wonder if my luggage will go missing/be hurled around so violently it's been broken, plus not wanting to faff around carrying anything very heavy.
When I have been on a holiday that e.g. requires black tie dress or a weird variety of different dress types then I do take checked baggage size luggage and the same for if I am traveling by car.