Hi,
Once you've stained the wood w/ your linseed oil, let it dry and if you want you can put a coat of paste wax on top of it. Wax is a moisture barrier and will give you an added layer of protection.depending on the weather where you live you may want to do this 2x a year. Also, w/ each coat of wax , the wood will get shinier.You can buy a can of johnsons paste wax for about $6.00 @ home depot. If you don't want to go that route, you can stain the wood, let it dry, and apply a product called Cetol. It is made by Sikkens. it has great uv protection and you will probably need to apply a coat once a year. I use this on doors and thresholds. Hope this helps, Keenan