At the other extreme, you have AA. Same livery for decades, doesn't seem at all outdated to me. Little to no paint (they use decals), reducing weight, maintenance (just replace the decals).
I believe the AA livery actually costs a fortune to maintain as aluminium will oxidize rougening the surface and causing drag if not polished regularly enough. It also means damage doesnt show up as easily. Modern paints weigh a lot less than of old and are easy to clean. Aircraft are rarely repainted just for a new livery, they'd be repainted every 4-5 years anyway. It took ages to get rid of the last world tail and that was just the tail.
AA will have to paint their 787s silver anyhow unless they like the raw carbon fibre look.