There are lots of methods for preserving cans. Starting from varnishing them. I would suggest that far cheaper then varnishing is to peel off the labels (but keep them orgaised in such a way that you know what everything is) and then just dip them into a can of cheap acrylic house-paint. Let dry and then dip in the other way up so you get total coverage. then write the contents on with indelible marker (add a date, or you will have archeological grade can five years form now, and they will still contain all the stuff you couldn''t face eating the first time).
You can also pack the cans into tupperware containers (they make a nice size that fits six cans). Duct-tape the boxes shut till you need them.
As for eggs.Try and buy them directly from a farm. Eggs that have been refrigerated last far less time then eggs that have always been room tempreture.
Some people like to paint the eggs with wax as this creates an impermeable barrier to air (eggshell actually breathes quite readily). You can also buy nifty plastic egg-storers from boating shops which lock together and make it easy to rotate several dozen eggs at a time safely (you should turn the eggs over every two days to get maximum life out of them). Keeping them in a the coolest part of the boat also helps.
Finally, some eggs just DO go bad. Carrying a kilo of powdered egg mix is not a bad idea, as it will let you use most of your recipes even if the fresh eggs all turn their toes up (or grow toes in the first place, for that matter).
Where in Oz are you sailing to?