I'm an SO on the Airbus fleet and it is quite different. I have never been asked to make bunks on the A340. Having said that, most of the flying now is on A330 so there are no crew rest bunks.
On the A330, it is 3 man crew. I always get involved (because I want to) and are quite often asked what fuel i would take if i was doing the sector as an FO.
I normally will ask if i can set up the FMS (6 out of 10 times I will get to). Not a requirement, but why not? I don't get to do much during the pre-start and pushback etc, so why not get involved where I can.
I guess it comes down to how keen you are. If you front up prepared as if you are doing the flight yourself, you'll never be caught off guard if you are asked to do something. Then when the upgrade comes around, you won't be doing much different during the pre-flight.
It would get very boring pretty quickly if you do nothing on every flight.