I'm not sure there are many, if any, international flights where you don't need to get off the plane when transiting even if it is the same flight - Singapore, Bangkok, Hong Kong and Dubai are ones where I have gotten off. I know Los Angeles needs pax on NZ1/2 to get off and I believe they even have to fill in immigration forms even though they are not landing in the US!
Re the tips about the shower, definitely worth it. Check to see what lounges are available and what facilities. Fresh set of clothes too helps. I did see someone get "gifted" a QF pair of F jammies while in Y once. She did look a little odd amongst the other pax, but I guess she was comfortable.