Lines...yeah sure, keep them separate. Taps, disconnects? IDK. I mean you should be sanitizing them anyway. Sanitary is sanitary. I have reused cobra taps and disconnects with no problem, but I fully dissasmeble them and treat them with hot PBW and StarSan.
The only o-ring/poppet that should come in contact with the beer is the liquid side poppet. I would not really worry about the o-rings. If you are worried that much, you could autoclave sterilize them (in a pressure caner).