Boring I know, but worth a look before bad things happen.
The aluminum spring nut used to set spring length on the rear shock can gall to the shock body if left in place too long without appropriate application of an anti-seize treatment. This can be an issue even if you don't ride in nasty conditions - I just removed the spring from a brand-new, never-used two year old Sachs shock and while the lock-ring spun free the spring nut stuck to the shock.
You may not like the nylon/composite spring nuts on Ohlins or WP shocks, but at least now you can see why they do it.