Rubber comes from a tree - even if the seal is made of a lot of non-rubber materials, there is still some; so, this means natural oils will be present - so also allot like tyres on the wheels.... ....if you hardly ride your bike, your tires (I'll re-spell that for ya) will last ages? ....umm, is that statement OK? Or would you think there may be a loss of traction in 2022 when you wheel her out and decide to cut come laps? Why? Could it be the out-gassing and lack of oils in the rubber that allows the correct degree of flex in the compound to promote traction? So, likewise, the shock seal or the fork seal, or even a plunger type steering damper seal, regardless of leaking will want/need changing periodically - there isn't that much we can do right now about our levels of technology. It needs flex to slide properly on the shaft surface.
Even if something is not leaking, it is not enough proof that the internal oils' molecular chains have not broken down or sheared into oblivion/burnt/turned into cat-pee - the oils besides doing a job of filming/lubricating, also provide cushioning (sort of the same thing) as well as the damping properties - I suppose if we talked of motor oils as needing changing only when the motor started to weep like a 1960's Triumph it might sound a little ridiculous, but to me this is how it is with suspensions!
Fluids can only ever be changed too often when the system takes undue stress in being manipulated apart and back together again during the oil-swapping processes. A design issue of course, and does not afflict our model of machine's fork type.
I know this is a thread from the depths, but it may still assist today...
