[spooph]

Concerning fluid - if it stays clean, there is no reason to change it out. I've re-used fork oil many times rebuilding various healthy forks, however, as soon as a seal fails, be it an end-seal or the tube seals, that oil becomes contaminated and needs to be purified. The oil itself won't break down, and were we able to purify it locally and re-use it it would be fine, but our only option is to switch it out.

Shocks are more resilient because they are typically less exposed to the elements. Forks get beaten up every time the bike goes out for a ride. Rubber breaks down, bad things get in there...