nope. I've not replaced anything in the year its been operating. I do suggest being gentle with the ball valves. They are poorly made and if you turn it too far it'll start to leak. More annoyingly it'll start sucking air through the gaps and make the filter loud.
Preserving o-rings is pretty simple. Get some silicone grease at the hardware store and cover your o-rings with em. Don't use petrol jelly simply because petrol products tend to decay rubbers and plastics. Silicone grease is reef safe and non-corrosive. It's like a very fine clay mixed with sillicone.