Good call on light and humidity; another factor is acid migration from wood or particleboard shelves which can hasten yellowing. Line the shelves with acid-free paper or a neutral barrier and keep the books away from exterior walls or heat vents which & yeah... lightly dust the page edges now and then, and for favorites, a deacidification spray can slow browning - spot-test first.
Evenings are when every lane is a traffic jam and the water's colder, which doesn't help nerves. Group classes can shove you along faster than your brain wants, and then you end up holding your breath and stiff as a board. Private is slower and pricier, but at least you can spend a whole session just learning to exhale and float without someone splashing past. Nose clips feel comforting but you'll want to ditch them once you can bubble steadily.
