Before you start remember that your bed will be subject to more wear than other parts of the vehicle, due to the entry of objects and the interperie, even partially. In addition to the load of the truck will depend on the weight. For what said this we advise the following.
Remove the snow with constancy, only if you live in an area with constant snowfall, or if it accumulates it is advisable to remove it so that it does not cause oxidation.
A lining in your bed liner can help preserve better and can also add weather resistance properties, some aerosols are powerful and will help this goal.
Another option in addition to the tonneau cover will always be to install a truck cap, although it loses aesthetics gains protection and storage, only recommended for people who do not care about the aesthetics of their truck.
Also protect the bottom of your truck, what happens on the top outside is important but oxidation can expand and it is recommended in all cases to apply the same spray on the bottom.