How long would you say the chair lasts before it starts to wear off lol
What wear off?
Are you asking how long the chair would last? If so then in the case of the Herman Miller Aeron's, lasting over 10 years is actually pretty common. There are probably ones that are still fine that are 20 years old as they came out in 1994.
Anyhow, it seems the DXRacer M series are reported as being the most comfortable, and the longer neck cushion is much better too.