My goto chair is the legendary Herman Miller Aeron. I've had my primary Aeron for >15 years and it still looks new, relatively inexpensive parts remain readily available on eBay and are easily user serviceable with a hex wrench. Aerons are built like tanks. They aren't cheap but no really high-quality, durable chair is cheap. The good news is that used Aerons are widely available.
A relatively newer chair that I'm using at my vacation house office is the Steelcase Gesture and I'm really liking it. IMHO, its best feature is the infinite adjustability of armrest position which is by far the best I've ever seen. However, the long-term comfort of the chair itself apparently varies by individual. I love it but I've read that, unlike the near-universally beloved Aeron, the Gesture just doesn't click with some people so be sure to give it a test drive first.
Kneeling chairs aid in keeping natural posture of spine.
I sit at my computer way too much, but I've never had problems with my back/neck like other people. It may be the way I sit: "leaning/slumping" back into my chair. (Most people seem to hunch forward).