they can certainly be replaced as part of preventative maintenance, though my rationale was that if it's not leaking, best not to mess with removing the tubes or spending $$$ right now since the time will come to part w/your wallet on some other repair.
compared to my wrx, it was a lot easier changing the plugs on the box, so it's not difficult to go back in again if you notice subsequent leaks. However, the tubes were a b$tch to remove. some folks have mentioned being able to pull them out by hand, mine seemed fused in. I saw a trick on pedro's garage about using the boat transom plug (which basically is a plug that you can cause to expand inside the plug tube by turning an attached t-fitting), but that didn't even work. I ended up making my own tool based upon a jury-rigged tool my local p-car dealership used and that finally did the trick. once they're out, it's easy to swap out the seals and re-install.
Threaded Mode
