not every ebay shock needs servicing/set-up.
Some riders appear to
Indeed you could get lucky and pick up a shock that’s come off an identical frame, and tuned for an identical rider.
In the other 99 cases out of 100 it’s either tuned for Mr Average on Average Bike Co’s Mediochre SLX, or already been tuned for someone/thing else.
There’s probably some inbetween grey areas, like picking up a NOS shock with the right tune, but it’s a fact that shocks need servicing occasionally, a shock that someones selling probably hasn’t just come back from a service or might even be faulty (there’s always a reason for selling), and custom tunes are relatively cheep.
The stock tune on my pitch was crap, a new air can went some way to solving that, it’s just come back from a custom tune at LOCO and it’s now a world apart from how the bike felt before (well, before before the damper split it’s guts).
Best £20 upgrade? Probably. Only downside is the lyrics feel like the weak link now!